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	$137.78	5.518%	$145.3827	$145.38	$145.40	$145.40
Purchase #2	$150.62	5.172%	$158.4101	$158.41	$158.40	$158.40
Purchase #3	$151.89	11.431%	$169.2525	$169.25	$169.25	$169.30
Purchase #4	$149.79	11.350%	$166.7912	$166.79	$166.80	$166.80
Purchase #5	$66.26	9.288%	$72.4142	$72.41	$72.40	$72.40
Purchase #6	$225.58	8.861%	$245.5686	$245.57	$245.55	$245.60
Purchase #7	$135.69	9.743%	$148.9103	$148.91	$148.90	$148.90
7 purchase totals =	$1,017.61		$1,106.7296	$1,106.72	$1,106.70	$1,106.80