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	$59.29	12.126%	$66.4795	$66.48	$66.50	$66.50
Purchase #2	$128.77	10.621%	$142.4467	$142.45	$142.45	$142.40
Purchase #3	$155.77	3.333%	$160.9618	$160.96	$160.95	$161.00
Purchase #4	$83.56	5.826%	$88.4282	$88.43	$88.45	$88.40
Purchase #5	$239.57	6.619%	$255.4271	$255.43	$255.45	$255.40
Purchase #6	$106.87	3.759%	$110.8872	$110.89	$110.90	$110.90
Purchase #7	$197.53	12.737%	$222.6894	$222.69	$222.70	$222.70
7 purchase totals =	$971.36		$1,047.3199	$1,047.33	$1,047.40	$1,047.30