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	$153.69	9.227%	$167.871	$167.87	$167.85	$167.90
Purchase #2	$120.90	9.243%	$132.0748	$132.07	$132.05	$132.10
Purchase #3	$229.66	3.455%	$237.5948	$237.59	$237.60	$237.60
Purchase #4	$114.85	9.316%	$125.5494	$125.55	$125.55	$125.50
Purchase #5	$20.28	4.456%	$21.1837	$21.18	$21.20	$21.20
Purchase #6	$92.69	13.483%	$105.1874	$105.19	$105.20	$105.20
Purchase #7	$53.74	9.813%	$59.0135	$59.01	$59.00	$59.00
7 purchase totals =	$785.81		$848.4746	$848.46	$848.45	$848.50