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	$238.81	10.689%	$264.3364	$264.34	$264.35	$264.30
Purchase #2	$92.36	12.641%	$104.0352	$104.04	$104.05	$104.00
Purchase #3	$149.61	10.161%	$164.8119	$164.81	$164.80	$164.80
Purchase #4	$171.51	7.456%	$184.2978	$184.30	$184.30	$184.30
Purchase #5	$50.88	7.676%	$54.7855	$54.79	$54.80	$54.80
Purchase #6	$40.74	6.771%	$43.4985	$43.50	$43.50	$43.50
Purchase #7	$190.63	8.184%	$206.2312	$206.23	$206.25	$206.20
7 purchase totals =	$934.54		$1,021.9965	$1,022.01	$1,022.05	$1,021.90