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	$59.64	3.242%	$61.5735	$61.57	$61.55	$61.60
Purchase #2	$202.47	7.819%	$218.3011	$218.30	$218.30	$218.30
Purchase #3	$208.43	9.541%	$228.3163	$228.32	$228.30	$228.30
Purchase #4	$219.83	3.325%	$227.1393	$227.14	$227.15	$227.10
Purchase #5	$160.82	5.857%	$170.2392	$170.24	$170.25	$170.20
Purchase #6	$207.63	11.455%	$231.414	$231.41	$231.40	$231.40
Purchase #7	$82.78	9.640%	$90.76	$90.76	$90.75	$90.80
7 purchase totals =	$1,141.60		$1,227.7434	$1,227.74	$1,227.70	$1,227.70