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	$205.95	3.185%	$212.5095	$212.51	$212.50	$212.50
Purchase #2	$240.45	11.264%	$267.5343	$267.53	$267.55	$267.50
Purchase #3	$167.79	10.345%	$185.1479	$185.15	$185.15	$185.10
Purchase #4	$42.58	9.612%	$46.6728	$46.67	$46.65	$46.70
Purchase #5	$37.86	11.192%	$42.0973	$42.10	$42.10	$42.10
Purchase #6	$18.73	5.142%	$19.6931	$19.69	$19.70	$19.70
Purchase #7	$215.66	8.557%	$234.114	$234.11	$234.10	$234.10
7 purchase totals =	$929.02		$1,007.7689	$1,007.76	$1,007.75	$1,007.70