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	$158.86	10.330%	$175.2702	$175.27	$175.25	$175.30
Purchase #2	$79.73	6.663%	$85.0424	$85.04	$85.05	$85.00
Purchase #3	$217.61	10.414%	$240.2719	$240.27	$240.25	$240.30
Purchase #4	$25.91	9.549%	$28.3841	$28.38	$28.40	$28.40
Purchase #5	$97.56	13.846%	$111.0682	$111.07	$111.05	$111.10
Purchase #6	$71.63	6.370%	$76.1928	$76.19	$76.20	$76.20
Purchase #7	$153.56	10.656%	$169.9234	$169.92	$169.90	$169.90
7 purchase totals =	$804.86		$886.1530	$886.14	$886.10	$886.20