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	$55.90	5.676%	$59.0729	$59.07	$59.05	$59.10
Purchase #2	$37.47	11.672%	$41.8435	$41.84	$41.85	$41.80
Purchase #3	$214.53	6.350%	$228.1527	$228.15	$228.15	$228.20
Purchase #4	$33.38	12.211%	$37.456	$37.46	$37.45	$37.50
Purchase #5	$122.90	11.703%	$137.283	$137.28	$137.30	$137.30
Purchase #6	$75.71	7.827%	$81.6358	$81.64	$81.65	$81.60
Purchase #7	$210.91	5.640%	$222.8053	$222.81	$222.80	$222.80
7 purchase totals =	$750.80		$808.2492	$808.25	$808.25	$808.30