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	$223.61	8.124%	$241.7761	$241.78	$241.80	$241.80
Purchase #2	$170.65	11.834%	$190.8447	$190.84	$190.85	$190.80
Purchase #3	$88.38	9.733%	$96.982	$96.98	$97.00	$97.00
Purchase #4	$105.84	7.542%	$113.8225	$113.82	$113.80	$113.80
Purchase #5	$245.51	13.850%	$279.5131	$279.51	$279.50	$279.50
Purchase #6	$39.85	4.203%	$41.5249	$41.52	$41.50	$41.50
Purchase #7	$130.74	7.584%	$140.6553	$140.66	$140.65	$140.70
7 purchase totals =	$1,004.58		$1,105.1186	$1,105.11	$1,105.10	$1,105.10