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	$151.90	13.336%	$172.1574	$172.16	$172.15	$172.20
Purchase #2	$155.25	13.377%	$176.0178	$176.02	$176.00	$176.00
Purchase #3	$153.74	11.363%	$171.2095	$171.21	$171.20	$171.20
Purchase #4	$30.80	9.311%	$33.6678	$33.67	$33.65	$33.70
Purchase #5	$150.51	3.324%	$155.513	$155.51	$155.50	$155.50
Purchase #6	$198.36	12.851%	$223.8512	$223.85	$223.85	$223.90
Purchase #7	$73.71	6.311%	$78.3618	$78.36	$78.35	$78.40
7 purchase totals =	$914.27		$1,010.7785	$1,010.78	$1,010.70	$1,010.90