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	$86.73	9.723%	$95.1628	$95.16	$95.15	$95.20
Purchase #2	$192.35	8.628%	$208.946	$208.95	$208.95	$208.90
Purchase #3	$71.53	9.502%	$78.3268	$78.33	$78.35	$78.30
Purchase #4	$193.85	8.275%	$209.8911	$209.89	$209.90	$209.90
Purchase #5	$98.37	7.225%	$105.4772	$105.48	$105.50	$105.50
Purchase #6	$67.63	10.280%	$74.5824	$74.58	$74.60	$74.60
Purchase #7	$49.39	11.673%	$55.1553	$55.16	$55.15	$55.20
7 purchase totals =	$759.85		$827.5416	$827.55	$827.60	$827.60