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	$106.35	9.799%	$116.7712	$116.77	$116.75	$116.80
Purchase #2	$111.43	11.584%	$124.3381	$124.34	$124.35	$124.30
Purchase #3	$63.71	12.811%	$71.8719	$71.87	$71.85	$71.90
Purchase #4	$152.83	6.489%	$162.7471	$162.75	$162.75	$162.70
Purchase #5	$92.67	12.468%	$104.2241	$104.22	$104.20	$104.20
Purchase #6	$131.83	11.103%	$146.4671	$146.47	$146.45	$146.50
Purchase #7	$225.31	11.483%	$251.1823	$251.18	$251.20	$251.20
7 purchase totals =	$884.13		$977.6018	$977.60	$977.55	$977.60