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	$246.60	3.774%	$255.9067	$255.91	$255.90	$255.90
Purchase #2	$186.35	5.282%	$196.193	$196.19	$196.20	$196.20
Purchase #3	$60.62	9.136%	$66.1582	$66.16	$66.15	$66.20
Purchase #4	$76.39	8.610%	$82.9672	$82.97	$82.95	$83.00
Purchase #5	$225.33	5.132%	$236.8939	$236.89	$236.90	$236.90
Purchase #6	$129.56	5.640%	$136.8672	$136.87	$136.85	$136.90
Purchase #7	$117.88	5.429%	$124.2797	$124.28	$124.30	$124.30
7 purchase totals =	$1,042.73		$1,099.2659	$1,099.27	$1,099.25	$1,099.40