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	$104.87	6.299%	$111.4758	$111.48	$111.50	$111.50
Purchase #2	$216.89	12.113%	$243.1619	$243.16	$243.15	$243.20
Purchase #3	$130.43	3.284%	$134.7133	$134.71	$134.70	$134.70
Purchase #4	$88.55	6.612%	$94.4049	$94.40	$94.40	$94.40
Purchase #5	$128.83	8.126%	$139.2987	$139.30	$139.30	$139.30
Purchase #6	$71.42	13.863%	$81.321	$81.32	$81.30	$81.30
Purchase #7	$215.28	6.283%	$228.806	$228.81	$228.80	$228.80
7 purchase totals =	$956.27		$1,033.1816	$1,033.18	$1,033.15	$1,033.20