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	$59.54	4.556%	$62.2526	$62.25	$62.25	$62.30
Purchase #2	$220.26	11.840%	$246.3388	$246.34	$246.35	$246.30
Purchase #3	$95.72	5.428%	$100.9157	$100.92	$100.90	$100.90
Purchase #4	$224.39	12.148%	$251.6489	$251.65	$251.65	$251.60
Purchase #5	$217.57	4.702%	$227.8001	$227.80	$227.80	$227.80
Purchase #6	$243.43	3.205%	$251.2319	$251.23	$251.25	$251.20
Purchase #7	$19.73	3.287%	$20.3785	$20.38	$20.40	$20.40
7 purchase totals =	$1,080.64		$1,160.5665	$1,160.57	$1,160.60	$1,160.50