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	$71.29	3.254%	$73.6098	$73.61	$73.60	$73.60
Purchase #2	$152.61	10.703%	$168.9438	$168.94	$168.95	$168.90
Purchase #3	$83.95	7.782%	$90.483	$90.48	$90.50	$90.50
Purchase #4	$140.93	7.220%	$151.1051	$151.11	$151.10	$151.10
Purchase #5	$92.78	6.784%	$99.0742	$99.07	$99.05	$99.10
Purchase #6	$159.56	6.828%	$170.4548	$170.45	$170.45	$170.50
Purchase #7	$191.40	11.566%	$213.5373	$213.54	$213.55	$213.50
7 purchase totals =	$892.52		$967.2080	$967.20	$967.20	$967.20