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	$210.39	5.828%	$222.6515	$222.65	$222.65	$222.70
Purchase #2	$235.52	10.557%	$260.3838	$260.38	$260.40	$260.40
Purchase #3	$145.71	11.830%	$162.9475	$162.95	$162.95	$162.90
Purchase #4	$124.44	5.386%	$131.1423	$131.14	$131.15	$131.10
Purchase #5	$66.51	9.576%	$72.879	$72.88	$72.90	$72.90
Purchase #6	$210.28	9.552%	$230.3659	$230.37	$230.35	$230.40
Purchase #7	$230.54	4.828%	$241.6705	$241.67	$241.65	$241.70
7 purchase totals =	$1,223.39		$1,322.0405	$1,322.04	$1,322.05	$1,322.10