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	$17.64	11.517%	$19.6716	$19.67	$19.65	$19.70
Purchase #2	$169.54	6.191%	$180.0362	$180.04	$180.05	$180.00
Purchase #3	$84.56	7.178%	$90.6297	$90.63	$90.65	$90.60
Purchase #4	$17.61	12.680%	$19.8429	$19.84	$19.85	$19.80
Purchase #5	$124.86	9.193%	$136.3384	$136.34	$136.35	$136.30
Purchase #6	$56.39	8.748%	$61.323	$61.32	$61.30	$61.30
Purchase #7	$203.29	9.501%	$222.6046	$222.60	$222.60	$222.60
7 purchase totals =	$673.89		$730.4464	$730.44	$730.45	$730.30