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	$205.49	3.625%	$212.939	$212.94	$212.95	$212.90
Purchase #2	$85.32	8.199%	$92.3154	$92.32	$92.30	$92.30
Purchase #3	$95.56	13.548%	$108.5065	$108.51	$108.50	$108.50
Purchase #4	$152.53	11.271%	$169.7217	$169.72	$169.70	$169.70
Purchase #5	$145.98	3.140%	$150.5638	$150.56	$150.55	$150.60
Purchase #6	$169.98	5.435%	$179.2184	$179.22	$179.20	$179.20
Purchase #7	$74.89	13.742%	$85.1814	$85.18	$85.20	$85.20
7 purchase totals =	$929.75		$998.4462	$998.45	$998.40	$998.40