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	$41.25	5.239%	$43.4111	$43.41	$43.40	$43.40
Purchase #2	$237.25	5.584%	$250.498	$250.50	$250.50	$250.50
Purchase #3	$143.57	10.848%	$159.1445	$159.14	$159.15	$159.10
Purchase #4	$183.54	12.461%	$206.4109	$206.41	$206.40	$206.40
Purchase #5	$155.75	6.508%	$165.8862	$165.89	$165.90	$165.90
Purchase #6	$225.67	7.650%	$242.9338	$242.93	$242.95	$242.90
Purchase #7	$150.36	3.343%	$155.3865	$155.39	$155.40	$155.40
7 purchase totals =	$1,137.39		$1,223.6710	$1,223.67	$1,223.70	$1,223.60