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	$69.76	6.562%	$74.3377	$74.34	$74.35	$74.30
Purchase #2	$110.30	5.282%	$116.126	$116.13	$116.15	$116.10
Purchase #3	$157.57	6.282%	$167.4685	$167.47	$167.45	$167.50
Purchase #4	$184.60	3.650%	$191.3379	$191.34	$191.35	$191.30
Purchase #5	$42.63	3.436%	$44.0948	$44.09	$44.10	$44.10
Purchase #6	$101.94	9.768%	$111.8975	$111.90	$111.90	$111.90
Purchase #7	$37.71	8.249%	$40.8207	$40.82	$40.80	$40.80
7 purchase totals =	$704.51		$746.0831	$746.09	$746.10	$746.00