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	$151.61	8.111%	$163.9071	$163.91	$163.90	$163.90
Purchase #2	$214.25	3.871%	$222.5436	$222.54	$222.55	$222.50
Purchase #3	$52.59	5.211%	$55.3305	$55.33	$55.35	$55.30
Purchase #4	$63.57	11.664%	$70.9848	$70.98	$71.00	$71.00
Purchase #5	$95.72	11.308%	$106.544	$106.54	$106.55	$106.50
Purchase #6	$122.57	6.157%	$130.1166	$130.12	$130.10	$130.10
Purchase #7	$244.30	7.371%	$262.3074	$262.31	$262.30	$262.30
7 purchase totals =	$944.61		$1,011.7340	$1,011.73	$1,011.75	$1,011.60