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	$93.28	11.147%	$103.6779	$103.68	$103.70	$103.70
Purchase #2	$50.77	5.287%	$53.4542	$53.45	$53.45	$53.50
Purchase #3	$78.83	13.595%	$89.5469	$89.55	$89.55	$89.50
Purchase #4	$140.34	4.865%	$147.1675	$147.17	$147.15	$147.20
Purchase #5	$48.84	9.826%	$53.639	$53.64	$53.65	$53.60
Purchase #6	$220.43	4.672%	$230.7285	$230.73	$230.75	$230.70
Purchase #7	$189.93	9.800%	$208.5431	$208.54	$208.55	$208.50
7 purchase totals =	$822.42		$886.7571	$886.76	$886.80	$886.70