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	$139.93	9.195%	$152.7966	$152.80	$152.80	$152.80
Purchase #2	$17.78	8.547%	$19.2997	$19.30	$19.30	$19.30
Purchase #3	$216.56	12.393%	$243.3983	$243.40	$243.40	$243.40
Purchase #4	$186.70	11.775%	$208.6839	$208.68	$208.70	$208.70
Purchase #5	$55.97	6.502%	$59.6092	$59.61	$59.60	$59.60
Purchase #6	$250.31	6.821%	$267.3836	$267.38	$267.40	$267.40
Purchase #7	$143.93	3.756%	$149.336	$149.34	$149.35	$149.30
7 purchase totals =	$1,011.18		$1,100.5073	$1,100.51	$1,100.55	$1,100.50