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	$235.52	6.830%	$251.606	$251.61	$251.60	$251.60
Purchase #2	$41.67	5.596%	$44.0019	$44.00	$44.00	$44.00
Purchase #3	$185.43	6.144%	$196.8228	$196.82	$196.80	$196.80
Purchase #4	$150.60	4.873%	$157.9387	$157.94	$157.95	$157.90
Purchase #5	$12.29	8.292%	$13.3091	$13.31	$13.30	$13.30
Purchase #6	$164.49	5.754%	$173.9548	$173.95	$173.95	$174.00
Purchase #7	$236.31	8.505%	$256.4082	$256.41	$256.40	$256.40
7 purchase totals =	$1,026.31		$1,094.0415	$1,094.04	$1,094.00	$1,094.00