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	$152.95	9.398%	$167.3242	$167.32	$167.30	$167.30
Purchase #2	$78.74	6.594%	$83.9321	$83.93	$83.95	$83.90
Purchase #3	$95.97	3.625%	$99.4489	$99.45	$99.45	$99.40
Purchase #4	$165.68	13.759%	$188.4759	$188.48	$188.50	$188.50
Purchase #5	$14.58	4.834%	$15.2848	$15.28	$15.30	$15.30
Purchase #6	$211.34	7.500%	$227.1905	$227.19	$227.20	$227.20
Purchase #7	$79.95	11.862%	$89.4337	$89.43	$89.45	$89.40
7 purchase totals =	$799.21		$871.0901	$871.08	$871.15	$871.00