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	$235.87	10.410%	$260.4241	$260.42	$260.40	$260.40
Purchase #2	$51.81	3.274%	$53.5063	$53.51	$53.50	$53.50
Purchase #3	$209.70	6.342%	$222.9992	$223.00	$223.00	$223.00
Purchase #4	$219.33	12.761%	$247.3187	$247.32	$247.30	$247.30
Purchase #5	$184.90	3.717%	$191.7727	$191.77	$191.75	$191.80
Purchase #6	$92.81	13.517%	$105.3551	$105.36	$105.35	$105.40
Purchase #7	$11.43	12.809%	$12.8941	$12.89	$12.90	$12.90
7 purchase totals =	$1,005.85		$1,094.2702	$1,094.27	$1,094.20	$1,094.30