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	$204.93	12.190%	$229.911	$229.91	$229.90	$229.90
Purchase #2	$60.95	10.598%	$67.4095	$67.41	$67.40	$67.40
Purchase #3	$172.34	9.155%	$188.1177	$188.12	$188.10	$188.10
Purchase #4	$244.75	9.167%	$267.1862	$267.19	$267.20	$267.20
Purchase #5	$94.88	6.199%	$100.7616	$100.76	$100.75	$100.80
Purchase #6	$41.92	4.292%	$43.7192	$43.72	$43.70	$43.70
Purchase #7	$50.78	3.263%	$52.437	$52.44	$52.45	$52.40
7 purchase totals =	$870.55		$949.5422	$949.55	$949.50	$949.50