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	$186.58	9.421%	$204.1577	$204.16	$204.15	$204.20
Purchase #2	$129.69	11.317%	$144.367	$144.37	$144.35	$144.40
Purchase #3	$142.82	11.380%	$159.0729	$159.07	$159.05	$159.10
Purchase #4	$33.29	11.275%	$37.0434	$37.04	$37.05	$37.00
Purchase #5	$29.31	12.326%	$32.9228	$32.92	$32.90	$32.90
Purchase #6	$244.93	5.468%	$258.3228	$258.32	$258.30	$258.30
Purchase #7	$236.57	9.783%	$259.7136	$259.71	$259.70	$259.70
7 purchase totals =	$1,003.19		$1,095.6002	$1,095.59	$1,095.50	$1,095.60