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	$83.68	7.155%	$89.6673	$89.67	$89.65	$89.70
Purchase #2	$56.36	7.222%	$60.4303	$60.43	$60.45	$60.40
Purchase #3	$116.73	11.797%	$130.5006	$130.50	$130.50	$130.50
Purchase #4	$22.31	6.794%	$23.8257	$23.83	$23.85	$23.80
Purchase #5	$31.66	11.636%	$35.344	$35.34	$35.35	$35.30
Purchase #6	$58.32	10.385%	$64.3765	$64.38	$64.40	$64.40
Purchase #7	$85.62	5.636%	$90.4455	$90.45	$90.45	$90.40
7 purchase totals =	$454.68		$494.5899	$494.60	$494.65	$494.50