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	$196.75	3.512%	$203.6599	$203.66	$203.65	$203.70
Purchase #2	$155.90	10.725%	$172.6203	$172.62	$172.60	$172.60
Purchase #3	$40.90	6.768%	$43.6681	$43.67	$43.65	$43.70
Purchase #4	$140.89	7.844%	$151.9414	$151.94	$151.95	$151.90
Purchase #5	$12.27	4.850%	$12.8651	$12.87	$12.85	$12.90
Purchase #6	$83.42	10.122%	$91.8638	$91.86	$91.85	$91.90
Purchase #7	$214.47	10.841%	$237.7207	$237.72	$237.70	$237.70
7 purchase totals =	$844.60		$914.3393	$914.34	$914.25	$914.40