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	$185.76	13.752%	$211.3057	$211.31	$211.30	$211.30
Purchase #2	$50.79	3.434%	$52.5341	$52.53	$52.55	$52.50
Purchase #3	$104.86	11.399%	$116.813	$116.81	$116.80	$116.80
Purchase #4	$197.74	12.298%	$222.0581	$222.06	$222.05	$222.10
Purchase #5	$89.48	13.240%	$101.3272	$101.33	$101.35	$101.30
Purchase #6	$204.30	6.871%	$218.3375	$218.34	$218.35	$218.30
Purchase #7	$105.79	4.438%	$110.485	$110.49	$110.50	$110.50
7 purchase totals =	$938.72		$1,032.8606	$1,032.87	$1,032.90	$1,032.80