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	$127.90	7.559%	$137.568	$137.57	$137.55	$137.60
Purchase #2	$30.63	4.551%	$32.024	$32.02	$32.00	$32.00
Purchase #3	$246.34	3.389%	$254.6885	$254.69	$254.70	$254.70
Purchase #4	$35.70	11.252%	$39.717	$39.72	$39.70	$39.70
Purchase #5	$159.46	5.361%	$168.0087	$168.01	$168.00	$168.00
Purchase #6	$45.74	11.152%	$50.8409	$50.84	$50.85	$50.80
Purchase #7	$208.37	4.361%	$217.457	$217.46	$217.45	$217.50
7 purchase totals =	$854.14		$900.3041	$900.31	$900.25	$900.30