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	$126.58	6.217%	$134.4495	$134.45	$134.45	$134.40
Purchase #2	$108.66	11.478%	$121.132	$121.13	$121.15	$121.10
Purchase #3	$152.34	5.601%	$160.8726	$160.87	$160.85	$160.90
Purchase #4	$239.92	10.156%	$264.2863	$264.29	$264.30	$264.30
Purchase #5	$235.61	13.609%	$267.6742	$267.67	$267.65	$267.70
Purchase #6	$185.50	6.139%	$196.8878	$196.89	$196.90	$196.90
Purchase #7	$12.91	6.377%	$13.7333	$13.73	$13.75	$13.70
7 purchase totals =	$1,061.52		$1,159.0357	$1,159.03	$1,159.05	$1,159.00