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	$172.66	4.142%	$179.8116	$179.81	$179.80	$179.80
Purchase #2	$185.92	13.533%	$211.0806	$211.08	$211.10	$211.10
Purchase #3	$40.37	12.112%	$45.2596	$45.26	$45.25	$45.30
Purchase #4	$104.35	8.317%	$113.0288	$113.03	$113.05	$113.00
Purchase #5	$108.50	9.340%	$118.6339	$118.63	$118.65	$118.60
Purchase #6	$153.60	9.749%	$168.5745	$168.57	$168.55	$168.60
Purchase #7	$109.76	4.324%	$114.506	$114.51	$114.50	$114.50
7 purchase totals =	$875.16		$950.8950	$950.89	$950.90	$950.90