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	$118.58	11.124%	$131.7708	$131.77	$131.75	$131.80
Purchase #2	$94.94	5.142%	$99.8218	$99.82	$99.80	$99.80
Purchase #3	$7.47	5.821%	$7.9048	$7.90	$7.90	$7.90
Purchase #4	$172.65	10.462%	$190.7126	$190.71	$190.70	$190.70
Purchase #5	$127.61	10.297%	$140.75	$140.75	$140.75	$140.80
Purchase #6	$246.48	13.652%	$280.1294	$280.13	$280.15	$280.10
Purchase #7	$193.87	10.209%	$213.6622	$213.66	$213.65	$213.70
7 purchase totals =	$961.60		$1,064.7516	$1,064.74	$1,064.70	$1,064.80