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	$199.75	13.716%	$227.1477	$227.15	$227.15	$227.10
Purchase #2	$223.53	12.505%	$251.4824	$251.48	$251.50	$251.50
Purchase #3	$65.43	7.833%	$70.5551	$70.56	$70.55	$70.60
Purchase #4	$55.59	3.581%	$57.5807	$57.58	$57.60	$57.60
Purchase #5	$213.45	4.589%	$223.2452	$223.25	$223.25	$223.20
Purchase #6	$53.60	11.726%	$59.8851	$59.89	$59.90	$59.90
Purchase #7	$121.95	11.829%	$136.3755	$136.38	$136.40	$136.40
7 purchase totals =	$933.30		$1,026.2717	$1,026.29	$1,026.35	$1,026.30