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	$141.31	9.127%	$154.2074	$154.21	$154.20	$154.20
Purchase #2	$137.85	7.348%	$147.9792	$147.98	$148.00	$148.00
Purchase #3	$52.99	13.479%	$60.1325	$60.13	$60.15	$60.10
Purchase #4	$204.73	6.617%	$218.277	$218.28	$218.30	$218.30
Purchase #5	$153.69	3.245%	$158.6772	$158.68	$158.70	$158.70
Purchase #6	$86.35	3.442%	$89.3222	$89.32	$89.30	$89.30
Purchase #7	$155.72	11.445%	$173.5422	$173.54	$173.55	$173.50
7 purchase totals =	$932.64		$1,002.1377	$1,002.14	$1,002.20	$1,002.10