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	$133.89	8.380%	$145.11	$145.11	$145.10	$145.10
Purchase #2	$135.33	7.117%	$144.9614	$144.96	$144.95	$145.00
Purchase #3	$208.86	9.843%	$229.4181	$229.42	$229.40	$229.40
Purchase #4	$150.32	4.767%	$157.4858	$157.49	$157.50	$157.50
Purchase #5	$50.32	13.429%	$57.0775	$57.08	$57.10	$57.10
Purchase #6	$38.41	6.519%	$40.9139	$40.91	$40.90	$40.90
Purchase #7	$90.57	10.568%	$100.1414	$100.14	$100.15	$100.10
7 purchase totals =	$807.70		$875.1081	$875.11	$875.10	$875.10