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	$119.44	11.661%	$133.3679	$133.37	$133.35	$133.40
Purchase #2	$145.41	4.442%	$151.8691	$151.87	$151.85	$151.90
Purchase #3	$173.85	5.303%	$183.0693	$183.07	$183.05	$183.10
Purchase #4	$79.32	7.802%	$85.5085	$85.51	$85.50	$85.50
Purchase #5	$130.90	12.315%	$147.0203	$147.02	$147.00	$147.00
Purchase #6	$104.40	13.659%	$118.66	$118.66	$118.65	$118.70
Purchase #7	$28.62	13.429%	$32.4634	$32.46	$32.45	$32.50
7 purchase totals =	$781.94		$851.9585	$851.96	$851.85	$852.10