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	$234.89	11.382%	$261.6252	$261.63	$261.65	$261.60
Purchase #2	$90.95	13.857%	$103.5529	$103.55	$103.55	$103.60
Purchase #3	$123.87	7.656%	$133.3535	$133.35	$133.35	$133.40
Purchase #4	$175.27	5.361%	$184.6662	$184.67	$184.65	$184.70
Purchase #5	$228.70	6.655%	$243.92	$243.92	$243.90	$243.90
Purchase #6	$119.59	10.228%	$131.8217	$131.82	$131.80	$131.80
Purchase #7	$168.85	3.261%	$174.3562	$174.36	$174.35	$174.40
7 purchase totals =	$1,142.12		$1,233.2957	$1,233.30	$1,233.25	$1,233.40