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	$56.62	4.327%	$59.0699	$59.07	$59.05	$59.10
Purchase #2	$204.35	6.585%	$217.8064	$217.81	$217.80	$217.80
Purchase #3	$44.43	12.616%	$50.0353	$50.04	$50.05	$50.00
Purchase #4	$134.46	3.377%	$139.0007	$139.00	$139.00	$139.00
Purchase #5	$230.48	9.811%	$253.0924	$253.09	$253.10	$253.10
Purchase #6	$216.52	13.208%	$245.118	$245.12	$245.10	$245.10
Purchase #7	$41.94	8.501%	$45.5053	$45.51	$45.50	$45.50
7 purchase totals =	$928.80		$1,009.6280	$1,009.64	$1,009.60	$1,009.60