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	$205.55	4.200%	$214.1831	$214.18	$214.20	$214.20
Purchase #2	$100.89	10.457%	$111.4401	$111.44	$111.45	$111.40
Purchase #3	$30.91	9.327%	$33.793	$33.79	$33.80	$33.80
Purchase #4	$250.88	8.773%	$272.8897	$272.89	$272.90	$272.90
Purchase #5	$59.88	11.649%	$66.8554	$66.86	$66.85	$66.90
Purchase #6	$236.98	10.870%	$262.7397	$262.74	$262.75	$262.70
Purchase #7	$119.99	3.520%	$124.2136	$124.21	$124.20	$124.20
7 purchase totals =	$1,005.08		$1,086.1146	$1,086.11	$1,086.15	$1,086.10