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	$38.46	7.127%	$41.201	$41.20	$41.20	$41.20
Purchase #2	$20.32	12.644%	$22.8893	$22.89	$22.90	$22.90
Purchase #3	$158.86	5.432%	$167.4893	$167.49	$167.50	$167.50
Purchase #4	$145.72	5.208%	$153.3091	$153.31	$153.30	$153.30
Purchase #5	$23.25	9.845%	$25.539	$25.54	$25.55	$25.50
Purchase #6	$245.46	5.316%	$258.5087	$258.51	$258.50	$258.50
Purchase #7	$33.91	6.561%	$36.1348	$36.13	$36.15	$36.10
7 purchase totals =	$665.98		$705.0712	$705.07	$705.10	$705.00