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	11.562%	$104.065	$104.07	$104.05	$104.10
Purchase #2	$184.95	6.479%	$196.9329	$196.93	$196.95	$196.90
Purchase #3	$210.43	8.557%	$228.4365	$228.44	$228.45	$228.40
Purchase #4	$59.78	3.576%	$61.9177	$61.92	$61.90	$61.90
Purchase #5	$199.57	11.536%	$222.5924	$222.59	$222.60	$222.60
Purchase #6	$122.34	3.558%	$126.6929	$126.69	$126.70	$126.70
Purchase #7	$188.33	9.352%	$205.9426	$205.94	$205.95	$205.90
7 purchase totals =	$1,058.68		$1,146.5800	$1,146.58	$1,146.60	$1,146.50