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	$200.68	12.445%	$225.6546	$225.65	$225.65	$225.70
Purchase #2	$95.53	12.783%	$107.7416	$107.74	$107.75	$107.70
Purchase #3	$132.38	10.643%	$146.4692	$146.47	$146.45	$146.50
Purchase #4	$37.27	12.351%	$41.8732	$41.87	$41.85	$41.90
Purchase #5	$227.80	7.623%	$245.1652	$245.17	$245.15	$245.20
Purchase #6	$214.34	3.818%	$222.5235	$222.52	$222.50	$222.50
Purchase #7	$240.98	10.146%	$265.4298	$265.43	$265.45	$265.40
7 purchase totals =	$1,148.98		$1,254.8571	$1,254.85	$1,254.80	$1,254.90