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	$231.96	13.281%	$262.7666	$262.77	$262.75	$262.80
Purchase #2	$42.62	7.164%	$45.6733	$45.67	$45.65	$45.70
Purchase #3	$110.30	6.286%	$117.2335	$117.23	$117.25	$117.20
Purchase #4	$174.54	12.322%	$196.0468	$196.05	$196.05	$196.00
Purchase #5	$23.44	3.352%	$24.2257	$24.23	$24.25	$24.20
Purchase #6	$157.85	6.551%	$168.1908	$168.19	$168.20	$168.20
Purchase #7	$103.53	8.625%	$112.4595	$112.46	$112.45	$112.50
7 purchase totals =	$844.24		$926.5962	$926.60	$926.60	$926.60