Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$218.34	6.851%	$233.2985	$233.30	$233.30	$233.30
Purchase #2	$196.93	12.751%	$222.0405	$222.04	$222.05	$222.00
Purchase #3	$155.67	13.130%	$176.1095	$176.11	$176.10	$176.10
Purchase #4	$169.25	10.256%	$186.6083	$186.61	$186.60	$186.60
Purchase #5	$156.60	5.285%	$164.8763	$164.88	$164.90	$164.90
Purchase #6	$162.33	7.727%	$174.8732	$174.87	$174.85	$174.90
Purchase #7	$168.33	12.146%	$188.7754	$188.78	$188.80	$188.80
7 purchase totals =	$1,227.45		$1,346.5817	$1,346.59	$1,346.60	$1,346.60