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	$10.45	11.670%	$11.6695	$11.67	$11.65	$11.70
Purchase #2	$194.53	7.504%	$209.1275	$209.13	$209.15	$209.10
Purchase #3	$135.83	3.430%	$140.489	$140.49	$140.50	$140.50
Purchase #4	$67.56	6.511%	$71.9588	$71.96	$71.95	$72.00
Purchase #5	$153.87	12.789%	$173.5484	$173.55	$173.55	$173.50
Purchase #6	$103.76	7.378%	$111.4154	$111.42	$111.40	$111.40
Purchase #7	$56.90	12.354%	$63.9294	$63.93	$63.95	$63.90
7 purchase totals =	$722.90		$782.1380	$782.15	$782.15	$782.10