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	$191.95	12.635%	$216.2029	$216.20	$216.20	$216.20
Purchase #2	$127.85	12.320%	$143.6011	$143.60	$143.60	$143.60
Purchase #3	$156.50	8.406%	$169.6554	$169.66	$169.65	$169.70
Purchase #4	$169.97	12.125%	$190.5789	$190.58	$190.60	$190.60
Purchase #5	$29.33	13.365%	$33.25	$33.25	$33.25	$33.30
Purchase #6	$205.44	8.817%	$223.5536	$223.55	$223.55	$223.60
Purchase #7	$89.59	5.298%	$94.3365	$94.34	$94.35	$94.30
7 purchase totals =	$970.63		$1,071.1784	$1,071.18	$1,071.20	$1,071.30