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	$6.82	7.447%	$7.3279	$7.33	$7.35	$7.30
Purchase #2	$92.70	10.298%	$102.2462	$102.25	$102.25	$102.20
Purchase #3	$75.75	10.121%	$83.4167	$83.42	$83.40	$83.40
Purchase #4	$245.58	4.352%	$256.2676	$256.27	$256.25	$256.30
Purchase #5	$76.39	8.592%	$82.9534	$82.95	$82.95	$83.00
Purchase #6	$135.58	6.410%	$144.2707	$144.27	$144.25	$144.30
Purchase #7	$36.29	3.518%	$37.5667	$37.57	$37.55	$37.60
7 purchase totals =	$669.11		$714.0492	$714.06	$714.00	$714.10