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	$43.50	3.367%	$44.9646	$44.96	$44.95	$45.00
Purchase #2	$100.81	5.397%	$106.2507	$106.25	$106.25	$106.30
Purchase #3	$236.38	5.816%	$250.1279	$250.13	$250.15	$250.10
Purchase #4	$150.56	11.111%	$167.2887	$167.29	$167.30	$167.30
Purchase #5	$93.35	5.388%	$98.3797	$98.38	$98.40	$98.40
Purchase #6	$32.35	10.235%	$35.661	$35.66	$35.65	$35.70
Purchase #7	$98.43	6.260%	$104.5917	$104.59	$104.60	$104.60
7 purchase totals =	$755.38		$807.2643	$807.26	$807.30	$807.40