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	$172.51	13.542%	$195.8713	$195.87	$195.85	$195.90
Purchase #2	$179.63	11.588%	$200.4455	$200.45	$200.45	$200.40
Purchase #3	$145.57	11.179%	$161.8433	$161.84	$161.85	$161.80
Purchase #4	$37.33	12.259%	$41.9063	$41.91	$41.90	$41.90
Purchase #5	$39.96	13.297%	$45.2735	$45.27	$45.25	$45.30
Purchase #6	$94.40	10.127%	$103.9599	$103.96	$103.95	$104.00
Purchase #7	$39.50	5.339%	$41.6089	$41.61	$41.60	$41.60
7 purchase totals =	$708.90		$790.9087	$790.91	$790.85	$790.90