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	$169.79	11.105%	$188.6452	$188.65	$188.65	$188.60
Purchase #2	$206.75	5.791%	$218.7229	$218.72	$218.70	$218.70
Purchase #3	$164.93	6.348%	$175.3998	$175.40	$175.40	$175.40
Purchase #4	$44.47	13.851%	$50.6295	$50.63	$50.65	$50.60
Purchase #5	$56.68	5.155%	$59.6019	$59.60	$59.60	$59.60
Purchase #6	$19.55	6.804%	$20.8802	$20.88	$20.90	$20.90
Purchase #7	$146.54	8.453%	$158.927	$158.93	$158.95	$158.90
7 purchase totals =	$808.71		$872.8065	$872.81	$872.85	$872.70