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	$39.61	5.874%	$41.9367	$41.94	$41.95	$41.90
Purchase #2	$245.71	13.160%	$278.0454	$278.05	$278.05	$278.00
Purchase #3	$83.86	3.313%	$86.6383	$86.64	$86.65	$86.60
Purchase #4	$99.64	11.691%	$111.2889	$111.29	$111.30	$111.30
Purchase #5	$36.92	8.110%	$39.9142	$39.91	$39.90	$39.90
Purchase #6	$131.44	3.760%	$136.3821	$136.38	$136.40	$136.40
Purchase #7	$146.45	7.420%	$157.3166	$157.32	$157.30	$157.30
7 purchase totals =	$783.63		$851.5222	$851.53	$851.55	$851.40