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	$64.61	4.215%	$67.3333	$67.33	$67.35	$67.30
Purchase #2	$180.44	8.841%	$196.3927	$196.39	$196.40	$196.40
Purchase #3	$37.34	10.427%	$41.2334	$41.23	$41.25	$41.20
Purchase #4	$221.38	12.445%	$248.9307	$248.93	$248.95	$248.90
Purchase #5	$231.82	12.331%	$260.4057	$260.41	$260.40	$260.40
Purchase #6	$151.78	13.180%	$171.7846	$171.78	$171.80	$171.80
Purchase #7	$77.69	10.261%	$85.6618	$85.66	$85.65	$85.70
7 purchase totals =	$965.06		$1,071.7422	$1,071.73	$1,071.80	$1,071.70