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	$160.54	9.353%	$175.5553	$175.56	$175.55	$175.60
Purchase #2	$70.79	10.213%	$78.0198	$78.02	$78.00	$78.00
Purchase #3	$32.53	3.437%	$33.6481	$33.65	$33.65	$33.60
Purchase #4	$9.47	11.847%	$10.5919	$10.59	$10.60	$10.60
Purchase #5	$28.89	7.293%	$30.9969	$31.00	$31.00	$31.00
Purchase #6	$216.72	4.163%	$225.7421	$225.74	$225.75	$225.70
Purchase #7	$116.57	11.377%	$129.8322	$129.83	$129.85	$129.80
7 purchase totals =	$635.51		$684.3863	$684.39	$684.40	$684.30