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	$197.89	7.303%	$212.3419	$212.34	$212.35	$212.30
Purchase #2	$109.37	13.596%	$124.2399	$124.24	$124.25	$124.20
Purchase #3	$116.89	9.616%	$128.1301	$128.13	$128.15	$128.10
Purchase #4	$213.83	11.618%	$238.6728	$238.67	$238.65	$238.70
Purchase #5	$44.29	7.136%	$47.4505	$47.45	$47.45	$47.50
Purchase #6	$124.33	5.273%	$130.8859	$130.89	$130.90	$130.90
Purchase #7	$60.30	3.767%	$62.5715	$62.57	$62.55	$62.60
7 purchase totals =	$866.90		$944.2926	$944.29	$944.30	$944.30