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	$134.83	13.820%	$153.4635	$153.46	$153.45	$153.50
Purchase #2	$126.70	10.354%	$139.8185	$139.82	$139.80	$139.80
Purchase #3	$176.35	5.282%	$185.6648	$185.66	$185.65	$185.70
Purchase #4	$130.57	7.642%	$140.5482	$140.55	$140.55	$140.50
Purchase #5	$130.81	12.458%	$147.1063	$147.11	$147.10	$147.10
Purchase #6	$210.37	11.173%	$233.8746	$233.87	$233.85	$233.90
Purchase #7	$17.93	6.560%	$19.1062	$19.11	$19.10	$19.10
7 purchase totals =	$927.56		$1,019.5821	$1,019.58	$1,019.50	$1,019.60