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	$153.25	12.215%	$171.9695	$171.97	$171.95	$172.00
Purchase #2	$121.35	3.571%	$125.6834	$125.68	$125.70	$125.70
Purchase #3	$216.29	4.163%	$225.2942	$225.29	$225.30	$225.30
Purchase #4	$61.66	10.165%	$67.9277	$67.93	$67.95	$67.90
Purchase #5	$66.47	8.665%	$72.2296	$72.23	$72.25	$72.20
Purchase #6	$73.47	12.498%	$82.6523	$82.65	$82.65	$82.70
Purchase #7	$230.49	10.825%	$255.4405	$255.44	$255.45	$255.40
7 purchase totals =	$922.98		$1,001.1972	$1,001.19	$1,001.25	$1,001.20