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	$180.42	9.123%	$196.8797	$196.88	$196.90	$196.90
Purchase #2	$37.64	3.725%	$39.0421	$39.04	$39.05	$39.00
Purchase #3	$17.47	10.268%	$19.2638	$19.26	$19.25	$19.30
Purchase #4	$47.36	6.680%	$50.5236	$50.52	$50.50	$50.50
Purchase #5	$7.53	3.142%	$7.7666	$7.77	$7.75	$7.80
Purchase #6	$19.73	4.629%	$20.6433	$20.64	$20.65	$20.60
Purchase #7	$131.72	6.730%	$140.5848	$140.58	$140.60	$140.60
7 purchase totals =	$441.87		$474.7039	$474.69	$474.70	$474.70