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	$82.74	3.723%	$85.8204	$85.82	$85.80	$85.80
Purchase #2	$32.86	12.625%	$37.0086	$37.01	$37.00	$37.00
Purchase #3	$169.49	7.738%	$182.6051	$182.61	$182.60	$182.60
Purchase #4	$96.37	3.794%	$100.0263	$100.03	$100.05	$100.00
Purchase #5	$33.48	4.760%	$35.0736	$35.07	$35.05	$35.10
Purchase #6	$147.51	5.360%	$155.4165	$155.42	$155.40	$155.40
Purchase #7	$156.36	3.175%	$161.3244	$161.32	$161.30	$161.30
7 purchase totals =	$718.81		$757.2749	$757.28	$757.20	$757.20