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	$223.60	13.651%	$254.1236	$254.12	$254.10	$254.10
Purchase #2	$23.44	8.746%	$25.4901	$25.49	$25.50	$25.50
Purchase #3	$148.63	13.536%	$168.7486	$168.75	$168.75	$168.70
Purchase #4	$30.89	4.221%	$32.1939	$32.19	$32.20	$32.20
Purchase #5	$79.57	8.725%	$86.5125	$86.51	$86.50	$86.50
Purchase #6	$225.71	5.868%	$238.9547	$238.95	$238.95	$239.00
Purchase #7	$196.54	13.241%	$222.5639	$222.56	$222.55	$222.60
7 purchase totals =	$928.38		$1,028.5873	$1,028.57	$1,028.55	$1,028.60