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	$123.91	5.475%	$130.6941	$130.69	$130.70	$130.70
Purchase #2	$172.30	8.518%	$186.9765	$186.98	$187.00	$187.00
Purchase #3	$159.96	5.604%	$168.9242	$168.92	$168.90	$168.90
Purchase #4	$34.78	13.409%	$39.4437	$39.44	$39.45	$39.40
Purchase #5	$64.91	11.711%	$72.5116	$72.51	$72.50	$72.50
Purchase #6	$120.76	8.385%	$130.8857	$130.89	$130.90	$130.90
Purchase #7	$71.58	4.631%	$74.8949	$74.89	$74.90	$74.90
7 purchase totals =	$748.20		$804.3307	$804.32	$804.35	$804.30