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	$239.27	12.521%	$269.229	$269.23	$269.25	$269.20
Purchase #2	$137.73	11.667%	$153.799	$153.80	$153.80	$153.80
Purchase #3	$208.90	9.417%	$228.5721	$228.57	$228.55	$228.60
Purchase #4	$45.54	11.648%	$50.8445	$50.84	$50.85	$50.80
Purchase #5	$113.45	12.805%	$127.9773	$127.98	$128.00	$128.00
Purchase #6	$152.45	4.196%	$158.8468	$158.85	$158.85	$158.80
Purchase #7	$66.77	8.816%	$72.6564	$72.66	$72.65	$72.70
7 purchase totals =	$964.11		$1,061.9251	$1,061.93	$1,061.95	$1,061.90