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	$100.49	4.614%	$105.1266	$105.13	$105.15	$105.10
Purchase #2	$80.57	13.849%	$91.7281	$91.73	$91.75	$91.70
Purchase #3	$45.41	10.804%	$50.3161	$50.32	$50.30	$50.30
Purchase #4	$43.86	4.629%	$45.8903	$45.89	$45.90	$45.90
Purchase #5	$75.81	8.868%	$82.5328	$82.53	$82.55	$82.50
Purchase #6	$9.70	12.315%	$10.8946	$10.89	$10.90	$10.90
Purchase #7	$140.99	11.672%	$157.4464	$157.45	$157.45	$157.40
7 purchase totals =	$496.83		$543.9349	$543.94	$544.00	$543.80