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	$108.43	11.655%	$121.0675	$121.07	$121.05	$121.10
Purchase #2	$48.33	7.867%	$52.1321	$52.13	$52.15	$52.10
Purchase #3	$141.48	4.557%	$147.9272	$147.93	$147.95	$147.90
Purchase #4	$9.61	4.465%	$10.0391	$10.04	$10.05	$10.00
Purchase #5	$185.55	8.223%	$200.8078	$200.81	$200.80	$200.80
Purchase #6	$114.50	11.336%	$127.4797	$127.48	$127.50	$127.50
Purchase #7	$196.47	10.616%	$217.3273	$217.33	$217.35	$217.30
7 purchase totals =	$804.37		$876.7807	$876.79	$876.85	$876.70