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	$43.63	3.435%	$45.1287	$45.13	$45.15	$45.10
Purchase #2	$150.43	12.436%	$169.1375	$169.14	$169.15	$169.10
Purchase #3	$159.66	13.222%	$180.7702	$180.77	$180.75	$180.80
Purchase #4	$66.60	6.222%	$70.7439	$70.74	$70.75	$70.70
Purchase #5	$165.67	3.776%	$171.9257	$171.93	$171.95	$171.90
Purchase #6	$36.49	13.827%	$41.5355	$41.54	$41.55	$41.50
Purchase #7	$242.59	3.268%	$250.5178	$250.52	$250.50	$250.50
7 purchase totals =	$865.07		$929.7593	$929.77	$929.80	$929.60