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	$88.38	8.102%	$95.5405	$95.54	$95.55	$95.50
Purchase #2	$127.34	7.168%	$136.4677	$136.47	$136.45	$136.50
Purchase #3	$240.25	3.140%	$247.7939	$247.79	$247.80	$247.80
Purchase #4	$52.79	4.113%	$54.9613	$54.96	$54.95	$55.00
Purchase #5	$25.34	12.562%	$28.5232	$28.52	$28.50	$28.50
Purchase #6	$159.72	8.272%	$172.932	$172.93	$172.95	$172.90
Purchase #7	$36.91	12.234%	$41.4256	$41.43	$41.45	$41.40
7 purchase totals =	$730.73		$777.6442	$777.64	$777.65	$777.60