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	$231.78	8.477%	$251.428	$251.43	$251.45	$251.40
Purchase #2	$168.94	12.840%	$190.6319	$190.63	$190.65	$190.60
Purchase #3	$210.59	10.122%	$231.9059	$231.91	$231.90	$231.90
Purchase #4	$35.72	4.846%	$37.451	$37.45	$37.45	$37.50
Purchase #5	$240.89	5.870%	$255.0302	$255.03	$255.05	$255.00
Purchase #6	$204.55	4.286%	$213.317	$213.32	$213.30	$213.30
Purchase #7	$229.35	3.645%	$237.7098	$237.71	$237.70	$237.70
7 purchase totals =	$1,321.82		$1,417.4738	$1,417.48	$1,417.50	$1,417.40