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	$206.51	7.743%	$222.5001	$222.50	$222.50	$222.50
Purchase #2	$208.34	3.501%	$215.634	$215.63	$215.65	$215.60
Purchase #3	$6.68	11.741%	$7.4643	$7.46	$7.45	$7.50
Purchase #4	$167.82	7.837%	$180.9721	$180.97	$180.95	$181.00
Purchase #5	$164.81	4.314%	$171.9199	$171.92	$171.90	$171.90
Purchase #6	$236.65	6.253%	$251.4477	$251.45	$251.45	$251.40
Purchase #7	$135.41	5.313%	$142.6043	$142.60	$142.60	$142.60
7 purchase totals =	$1,126.22		$1,192.5424	$1,192.53	$1,192.50	$1,192.50