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	$129.44	7.821%	$139.5635	$139.56	$139.55	$139.60
Purchase #2	$229.77	6.810%	$245.4173	$245.42	$245.40	$245.40
Purchase #3	$6.72	8.490%	$7.2905	$7.29	$7.30	$7.30
Purchase #4	$227.62	6.580%	$242.5974	$242.60	$242.60	$242.60
Purchase #5	$35.77	13.220%	$40.4988	$40.50	$40.50	$40.50
Purchase #6	$88.90	13.676%	$101.058	$101.06	$101.05	$101.10
Purchase #7	$247.29	5.362%	$260.5497	$260.55	$260.55	$260.50
7 purchase totals =	$965.51		$1,036.9752	$1,036.98	$1,036.95	$1,037.00