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	$59.34	13.262%	$67.2097	$67.21	$67.20	$67.20
Purchase #2	$133.95	11.671%	$149.5833	$149.58	$149.60	$149.60
Purchase #3	$167.53	12.629%	$188.6874	$188.69	$188.70	$188.70
Purchase #4	$247.76	4.869%	$259.8234	$259.82	$259.80	$259.80
Purchase #5	$25.53	13.372%	$28.9439	$28.94	$28.95	$28.90
Purchase #6	$243.87	5.811%	$258.0413	$258.04	$258.05	$258.00
Purchase #7	$105.82	3.508%	$109.5322	$109.53	$109.55	$109.50
7 purchase totals =	$983.80		$1,061.8212	$1,061.81	$1,061.85	$1,061.70