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	$40.81	11.108%	$45.3432	$45.34	$45.35	$45.30
Purchase #2	$226.85	6.695%	$242.0376	$242.04	$242.05	$242.00
Purchase #3	$150.35	8.290%	$162.814	$162.81	$162.80	$162.80
Purchase #4	$155.50	5.797%	$164.5143	$164.51	$164.50	$164.50
Purchase #5	$160.34	5.771%	$169.5932	$169.59	$169.60	$169.60
Purchase #6	$18.47	13.228%	$20.9132	$20.91	$20.90	$20.90
Purchase #7	$247.37	9.118%	$269.9252	$269.93	$269.95	$269.90
7 purchase totals =	$999.69		$1,075.1407	$1,075.13	$1,075.15	$1,075.00