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	$185.66	7.790%	$200.1229	$200.12	$200.10	$200.10
Purchase #2	$73.59	12.793%	$83.0044	$83.00	$83.00	$83.00
Purchase #3	$122.54	3.507%	$126.8375	$126.84	$126.85	$126.80
Purchase #4	$39.25	10.821%	$43.4972	$43.50	$43.50	$43.50
Purchase #5	$142.90	11.510%	$159.3478	$159.35	$159.35	$159.30
Purchase #6	$49.53	10.327%	$54.645	$54.65	$54.65	$54.60
Purchase #7	$116.49	13.273%	$131.9517	$131.95	$131.95	$132.00
7 purchase totals =	$729.96		$799.4065	$799.41	$799.40	$799.30