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	$131.85	13.418%	$149.5416	$149.54	$149.55	$149.50
Purchase #2	$37.29	12.668%	$42.0139	$42.01	$42.00	$42.00
Purchase #3	$156.86	5.120%	$164.8912	$164.89	$164.90	$164.90
Purchase #4	$250.61	7.422%	$269.2103	$269.21	$269.20	$269.20
Purchase #5	$192.49	3.533%	$199.2907	$199.29	$199.30	$199.30
Purchase #6	$46.69	13.871%	$53.1664	$53.17	$53.15	$53.20
Purchase #7	$217.58	11.426%	$242.4407	$242.44	$242.45	$242.40
7 purchase totals =	$1,033.37		$1,120.5548	$1,120.55	$1,120.55	$1,120.50