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	$54.88	4.461%	$57.3282	$57.33	$57.35	$57.30
Purchase #2	$224.54	13.207%	$254.195	$254.20	$254.20	$254.20
Purchase #3	$122.45	5.251%	$128.8798	$128.88	$128.90	$128.90
Purchase #4	$228.47	11.872%	$255.594	$255.59	$255.60	$255.60
Purchase #5	$66.35	5.797%	$70.1963	$70.20	$70.20	$70.20
Purchase #6	$92.45	6.109%	$98.0978	$98.10	$98.10	$98.10
Purchase #7	$166.74	9.456%	$182.5069	$182.51	$182.50	$182.50
7 purchase totals =	$955.88		$1,046.7980	$1,046.81	$1,046.85	$1,046.80