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	$100.67	5.226%	$105.931	$105.93	$105.95	$105.90
Purchase #2	$138.42	12.173%	$155.2699	$155.27	$155.25	$155.30
Purchase #3	$102.53	9.526%	$112.297	$112.30	$112.30	$112.30
Purchase #4	$8.63	6.304%	$9.174	$9.17	$9.15	$9.20
Purchase #5	$231.41	13.620%	$262.928	$262.93	$262.95	$262.90
Purchase #6	$83.30	7.109%	$89.2218	$89.22	$89.20	$89.20
Purchase #7	$190.83	13.275%	$216.1627	$216.16	$216.15	$216.20
7 purchase totals =	$855.79		$950.9844	$950.98	$950.95	$951.00