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	$184.27	3.181%	$190.1316	$190.13	$190.15	$190.10
Purchase #2	$64.96	11.120%	$72.1836	$72.18	$72.20	$72.20
Purchase #3	$106.32	11.245%	$118.2757	$118.28	$118.30	$118.30
Purchase #4	$186.81	13.355%	$211.7585	$211.76	$211.75	$211.80
Purchase #5	$172.57	13.825%	$196.4278	$196.43	$196.45	$196.40
Purchase #6	$97.72	12.604%	$110.0366	$110.04	$110.05	$110.00
Purchase #7	$31.77	7.229%	$34.0667	$34.07	$34.05	$34.10
7 purchase totals =	$844.42		$932.8805	$932.89	$932.95	$932.90