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	$230.45	5.824%	$243.8714	$243.87	$243.85	$243.90
Purchase #2	$46.96	7.198%	$50.3402	$50.34	$50.35	$50.30
Purchase #3	$165.60	4.375%	$172.845	$172.85	$172.85	$172.80
Purchase #4	$79.26	7.260%	$85.0143	$85.01	$85.00	$85.00
Purchase #5	$11.84	13.140%	$13.3958	$13.40	$13.40	$13.40
Purchase #6	$82.30	7.666%	$88.6091	$88.61	$88.60	$88.60
Purchase #7	$99.30	7.243%	$106.4923	$106.49	$106.50	$106.50
7 purchase totals =	$715.71		$760.5681	$760.57	$760.55	$760.50