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	$167.67	10.615%	$185.4682	$185.47	$185.45	$185.50
Purchase #2	$39.83	7.199%	$42.6974	$42.70	$42.70	$42.70
Purchase #3	$64.46	3.469%	$66.6961	$66.70	$66.70	$66.70
Purchase #4	$67.84	3.692%	$70.3447	$70.34	$70.35	$70.30
Purchase #5	$36.57	11.811%	$40.8893	$40.89	$40.90	$40.90
Purchase #6	$232.54	13.303%	$263.4748	$263.47	$263.45	$263.50
Purchase #7	$232.27	12.612%	$261.5639	$261.56	$261.55	$261.60
7 purchase totals =	$841.18		$931.1344	$931.13	$931.10	$931.20