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	$121.78	8.591%	$132.2421	$132.24	$132.25	$132.20
Purchase #2	$150.40	3.359%	$155.4519	$155.45	$155.45	$155.50
Purchase #3	$7.89	9.268%	$8.6212	$8.62	$8.60	$8.60
Purchase #4	$60.57	5.481%	$63.8898	$63.89	$63.90	$63.90
Purchase #5	$72.79	13.569%	$82.6669	$82.67	$82.65	$82.70
Purchase #6	$35.33	6.119%	$37.4918	$37.49	$37.50	$37.50
Purchase #7	$244.47	11.467%	$272.5034	$272.50	$272.50	$272.50
7 purchase totals =	$693.23		$752.8671	$752.86	$752.85	$752.90