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	$182.69	3.362%	$188.832	$188.83	$188.85	$188.80
Purchase #2	$31.89	12.255%	$35.7981	$35.80	$35.80	$35.80
Purchase #3	$11.54	13.500%	$13.0979	$13.10	$13.10	$13.10
Purchase #4	$78.51	10.318%	$86.6107	$86.61	$86.60	$86.60
Purchase #5	$244.92	12.382%	$275.246	$275.25	$275.25	$275.20
Purchase #6	$164.57	3.794%	$170.8138	$170.81	$170.80	$170.80
Purchase #7	$220.54	13.197%	$249.6447	$249.64	$249.65	$249.60
7 purchase totals =	$934.66		$1,020.0432	$1,020.04	$1,020.05	$1,019.90