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	$104.51	7.115%	$111.9459	$111.95	$111.95	$111.90
Purchase #2	$152.86	8.575%	$165.9677	$165.97	$165.95	$166.00
Purchase #3	$249.73	9.865%	$274.3659	$274.37	$274.35	$274.40
Purchase #4	$41.47	13.136%	$46.9175	$46.92	$46.90	$46.90
Purchase #5	$124.79	12.704%	$140.6433	$140.64	$140.65	$140.60
Purchase #6	$235.41	10.575%	$260.3046	$260.30	$260.30	$260.30
Purchase #7	$34.38	10.113%	$37.8568	$37.86	$37.85	$37.90
7 purchase totals =	$943.15		$1,038.0017	$1,038.01	$1,037.95	$1,038.00