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	$170.55	13.275%	$193.1905	$193.19	$193.20	$193.20
Purchase #2	$149.81	4.734%	$156.902	$156.90	$156.90	$156.90
Purchase #3	$131.80	13.295%	$149.3228	$149.32	$149.30	$149.30
Purchase #4	$152.79	9.632%	$167.5067	$167.51	$167.50	$167.50
Purchase #5	$182.82	7.644%	$196.7948	$196.79	$196.80	$196.80
Purchase #6	$137.78	4.421%	$143.8713	$143.87	$143.85	$143.90
Purchase #7	$235.28	4.862%	$246.7193	$246.72	$246.70	$246.70
7 purchase totals =	$1,160.83		$1,254.3074	$1,254.30	$1,254.25	$1,254.30