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	$93.83	3.123%	$96.7603	$96.76	$96.75	$96.80
Purchase #2	$122.83	8.379%	$133.1219	$133.12	$133.10	$133.10
Purchase #3	$230.49	11.344%	$256.6368	$256.64	$256.65	$256.60
Purchase #4	$65.63	6.130%	$69.6531	$69.65	$69.65	$69.70
Purchase #5	$158.47	6.337%	$168.5122	$168.51	$168.50	$168.50
Purchase #6	$178.83	12.320%	$200.8619	$200.86	$200.85	$200.90
Purchase #7	$49.83	12.180%	$55.8993	$55.90	$55.90	$55.90
7 purchase totals =	$899.91		$981.4455	$981.44	$981.40	$981.50