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	$195.98	13.242%	$221.9317	$221.93	$221.95	$221.90
Purchase #2	$121.53	4.616%	$127.1398	$127.14	$127.15	$127.10
Purchase #3	$100.38	4.602%	$104.9995	$105.00	$105.00	$105.00
Purchase #4	$137.76	10.373%	$152.0498	$152.05	$152.05	$152.00
Purchase #5	$208.71	7.104%	$223.5368	$223.54	$223.55	$223.50
Purchase #6	$38.82	4.567%	$40.5929	$40.59	$40.60	$40.60
Purchase #7	$69.28	6.735%	$73.946	$73.95	$73.95	$73.90
7 purchase totals =	$872.46		$944.1965	$944.20	$944.25	$944.00