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	$228.37	11.387%	$254.3745	$254.37	$254.35	$254.40
Purchase #2	$217.96	6.218%	$231.5128	$231.51	$231.50	$231.50
Purchase #3	$135.62	13.427%	$153.8297	$153.83	$153.85	$153.80
Purchase #4	$40.42	4.653%	$42.3007	$42.30	$42.30	$42.30
Purchase #5	$126.34	10.632%	$139.7725	$139.77	$139.75	$139.80
Purchase #6	$102.31	11.744%	$114.3253	$114.33	$114.35	$114.30
Purchase #7	$149.41	12.699%	$168.3836	$168.38	$168.40	$168.40
7 purchase totals =	$1,000.43		$1,104.4991	$1,104.49	$1,104.50	$1,104.50