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	$12.95	11.731%	$14.4692	$14.47	$14.45	$14.50
Purchase #2	$220.95	13.518%	$250.818	$250.82	$250.80	$250.80
Purchase #3	$51.98	13.790%	$59.148	$59.15	$59.15	$59.10
Purchase #4	$176.73	3.284%	$182.5338	$182.53	$182.55	$182.50
Purchase #5	$120.84	7.403%	$129.7858	$129.79	$129.80	$129.80
Purchase #6	$100.79	10.767%	$111.6421	$111.64	$111.65	$111.60
Purchase #7	$187.25	3.168%	$193.1821	$193.18	$193.20	$193.20
7 purchase totals =	$871.49		$941.5790	$941.58	$941.60	$941.50