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	$196.35	3.760%	$203.7328	$203.73	$203.75	$203.70
Purchase #2	$72.42	13.751%	$82.3785	$82.38	$82.40	$82.40
Purchase #3	$227.33	13.807%	$258.7175	$258.72	$258.70	$258.70
Purchase #4	$40.49	7.332%	$43.4587	$43.46	$43.45	$43.50
Purchase #5	$113.31	6.746%	$120.9539	$120.95	$120.95	$121.00
Purchase #6	$130.35	4.476%	$136.1845	$136.18	$136.20	$136.20
Purchase #7	$199.98	8.765%	$217.5082	$217.51	$217.50	$217.50
7 purchase totals =	$980.23		$1,062.9341	$1,062.93	$1,062.95	$1,063.00