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	$141.50	10.225%	$155.9684	$155.97	$155.95	$156.00
Purchase #2	$53.37	4.229%	$55.627	$55.63	$55.65	$55.60
Purchase #3	$127.81	11.565%	$142.5912	$142.59	$142.60	$142.60
Purchase #4	$157.49	5.345%	$165.9078	$165.91	$165.90	$165.90
Purchase #5	$25.62	12.397%	$28.7961	$28.80	$28.80	$28.80
Purchase #6	$86.48	11.668%	$96.5705	$96.57	$96.55	$96.60
Purchase #7	$236.56	8.399%	$256.4287	$256.43	$256.45	$256.40
7 purchase totals =	$828.83		$901.8897	$901.90	$901.90	$901.90