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	$131.37	8.522%	$142.5654	$142.57	$142.55	$142.60
Purchase #2	$77.99	11.675%	$87.0953	$87.10	$87.10	$87.10
Purchase #3	$104.61	8.422%	$113.4203	$113.42	$113.40	$113.40
Purchase #4	$55.35	10.510%	$61.1673	$61.17	$61.15	$61.20
Purchase #5	$40.47	12.231%	$45.4199	$45.42	$45.40	$45.40
Purchase #6	$89.84	5.494%	$94.7758	$94.78	$94.80	$94.80
Purchase #7	$177.70	12.571%	$200.0387	$200.04	$200.05	$200.00
7 purchase totals =	$677.33		$744.4827	$744.50	$744.45	$744.50