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	$55.94	6.673%	$59.6729	$59.67	$59.65	$59.70
Purchase #2	$125.86	12.508%	$141.6026	$141.60	$141.60	$141.60
Purchase #3	$35.49	4.475%	$37.0782	$37.08	$37.10	$37.10
Purchase #4	$144.64	8.674%	$157.1861	$157.19	$157.20	$157.20
Purchase #5	$172.48	10.844%	$191.1837	$191.18	$191.20	$191.20
Purchase #6	$46.91	11.481%	$52.2957	$52.30	$52.30	$52.30
Purchase #7	$149.90	12.375%	$168.4501	$168.45	$168.45	$168.50
7 purchase totals =	$731.22		$807.4693	$807.47	$807.50	$807.60