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	$81.47	4.811%	$85.3895	$85.39	$85.40	$85.40
Purchase #2	$121.27	3.454%	$125.4587	$125.46	$125.45	$125.50
Purchase #3	$33.94	5.229%	$35.7147	$35.71	$35.70	$35.70
Purchase #4	$77.95	5.282%	$82.0673	$82.07	$82.05	$82.10
Purchase #5	$121.98	9.525%	$133.5986	$133.60	$133.60	$133.60
Purchase #6	$45.41	13.404%	$51.4968	$51.50	$51.50	$51.50
Purchase #7	$30.64	6.821%	$32.73	$32.73	$32.75	$32.70
7 purchase totals =	$512.66		$546.4556	$546.46	$546.45	$546.50