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	$157.54	6.519%	$167.81	$167.81	$167.80	$167.80
Purchase #2	$87.39	3.787%	$90.6995	$90.70	$90.70	$90.70
Purchase #3	$62.65	10.581%	$69.279	$69.28	$69.30	$69.30
Purchase #4	$82.68	9.204%	$90.2899	$90.29	$90.30	$90.30
Purchase #5	$137.96	9.470%	$151.0248	$151.02	$151.00	$151.00
Purchase #6	$110.71	6.301%	$117.6858	$117.69	$117.70	$117.70
Purchase #7	$101.46	11.481%	$113.1086	$113.11	$113.10	$113.10
7 purchase totals =	$740.39		$799.8976	$799.90	$799.90	$799.90