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	$246.53	7.149%	$264.1544	$264.15	$264.15	$264.20
Purchase #2	$148.66	4.730%	$155.6916	$155.69	$155.70	$155.70
Purchase #3	$138.46	4.637%	$144.8804	$144.88	$144.90	$144.90
Purchase #4	$225.77	12.291%	$253.5194	$253.52	$253.50	$253.50
Purchase #5	$138.31	6.115%	$146.7677	$146.77	$146.75	$146.80
Purchase #6	$166.91	13.140%	$188.842	$188.84	$188.85	$188.80
Purchase #7	$223.66	3.566%	$231.6357	$231.64	$231.65	$231.60
7 purchase totals =	$1,288.30		$1,385.4912	$1,385.49	$1,385.50	$1,385.50