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	$72.80	7.197%	$78.0394	$78.04	$78.05	$78.00
Purchase #2	$129.83	8.231%	$140.5163	$140.52	$140.50	$140.50
Purchase #3	$39.61	11.344%	$44.1034	$44.10	$44.10	$44.10
Purchase #4	$222.35	4.134%	$231.5419	$231.54	$231.55	$231.50
Purchase #5	$105.50	9.444%	$115.4634	$115.46	$115.45	$115.50
Purchase #6	$216.80	7.830%	$233.7754	$233.78	$233.80	$233.80
Purchase #7	$165.71	4.653%	$173.4205	$173.42	$173.40	$173.40
7 purchase totals =	$952.60		$1,016.8603	$1,016.86	$1,016.85	$1,016.80