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	$116.90	12.439%	$131.4412	$131.44	$131.45	$131.40
Purchase #2	$137.40	10.445%	$151.7514	$151.75	$151.75	$151.80
Purchase #3	$219.62	10.825%	$243.3939	$243.39	$243.40	$243.40
Purchase #4	$70.37	3.127%	$72.5705	$72.57	$72.55	$72.60
Purchase #5	$48.56	3.400%	$50.211	$50.21	$50.20	$50.20
Purchase #6	$28.68	11.373%	$31.9418	$31.94	$31.95	$31.90
Purchase #7	$153.83	11.198%	$171.0559	$171.06	$171.05	$171.10
7 purchase totals =	$775.36		$852.3657	$852.36	$852.35	$852.40