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	$213.92	8.326%	$231.731	$231.73	$231.75	$231.70
Purchase #2	$36.50	11.444%	$40.6771	$40.68	$40.70	$40.70
Purchase #3	$244.46	5.782%	$258.5947	$258.59	$258.60	$258.60
Purchase #4	$39.72	11.710%	$44.3712	$44.37	$44.35	$44.40
Purchase #5	$80.79	3.576%	$83.6791	$83.68	$83.70	$83.70
Purchase #6	$72.31	13.604%	$82.1471	$82.15	$82.15	$82.10
Purchase #7	$125.83	4.541%	$131.5439	$131.54	$131.55	$131.50
7 purchase totals =	$813.53		$872.7441	$872.74	$872.80	$872.70