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	$38.47	11.634%	$42.9456	$42.95	$42.95	$42.90
Purchase #2	$244.71	9.467%	$267.8767	$267.88	$267.90	$267.90
Purchase #3	$162.25	12.333%	$182.2603	$182.26	$182.25	$182.30
Purchase #4	$91.41	8.485%	$99.1661	$99.17	$99.15	$99.20
Purchase #5	$69.88	5.269%	$73.562	$73.56	$73.55	$73.60
Purchase #6	$97.66	7.812%	$105.2892	$105.29	$105.30	$105.30
Purchase #7	$171.43	5.148%	$180.2552	$180.26	$180.25	$180.30
7 purchase totals =	$875.81		$951.3551	$951.37	$951.35	$951.50