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	$53.93	11.376%	$60.0651	$60.07	$60.05	$60.10
Purchase #2	$172.43	10.489%	$190.5162	$190.52	$190.50	$190.50
Purchase #3	$163.47	5.146%	$171.8822	$171.88	$171.90	$171.90
Purchase #4	$188.29	6.691%	$200.8885	$200.89	$200.90	$200.90
Purchase #5	$189.43	4.676%	$198.2877	$198.29	$198.30	$198.30
Purchase #6	$64.61	13.180%	$73.1256	$73.13	$73.15	$73.10
Purchase #7	$216.25	13.490%	$245.4221	$245.42	$245.40	$245.40
7 purchase totals =	$1,048.41		$1,140.1874	$1,140.20	$1,140.20	$1,140.20