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	$172.90	7.230%	$185.4007	$185.40	$185.40	$185.40
Purchase #2	$95.73	7.297%	$102.7154	$102.72	$102.70	$102.70
Purchase #3	$33.82	10.248%	$37.2859	$37.29	$37.30	$37.30
Purchase #4	$109.51	12.596%	$123.3039	$123.30	$123.30	$123.30
Purchase #5	$87.62	8.598%	$95.1536	$95.15	$95.15	$95.20
Purchase #6	$186.99	12.330%	$210.0459	$210.05	$210.05	$210.00
Purchase #7	$219.89	11.409%	$244.9773	$244.98	$245.00	$245.00
7 purchase totals =	$906.46		$998.8827	$998.89	$998.90	$998.90