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	$210.67	7.204%	$225.8467	$225.85	$225.85	$225.80
Purchase #2	$142.79	5.233%	$150.2622	$150.26	$150.25	$150.30
Purchase #3	$249.85	9.853%	$274.4677	$274.47	$274.45	$274.50
Purchase #4	$153.39	7.135%	$164.3344	$164.33	$164.35	$164.30
Purchase #5	$225.39	11.870%	$252.1438	$252.14	$252.15	$252.10
Purchase #6	$6.68	3.279%	$6.899	$6.90	$6.90	$6.90
Purchase #7	$6.87	6.546%	$7.3197	$7.32	$7.30	$7.30
7 purchase totals =	$995.64		$1,081.2735	$1,081.27	$1,081.25	$1,081.20