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	$41.38	12.405%	$46.5132	$46.51	$46.50	$46.50
Purchase #2	$245.85	10.772%	$272.333	$272.33	$272.35	$272.30
Purchase #3	$145.46	5.589%	$153.5898	$153.59	$153.60	$153.60
Purchase #4	$124.47	5.110%	$130.8304	$130.83	$130.85	$130.80
Purchase #5	$174.55	12.586%	$196.5189	$196.52	$196.50	$196.50
Purchase #6	$200.34	8.183%	$216.7338	$216.73	$216.75	$216.70
Purchase #7	$218.98	13.517%	$248.5795	$248.58	$248.60	$248.60
7 purchase totals =	$1,151.03		$1,265.0986	$1,265.09	$1,265.15	$1,265.00