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	$127.67	7.670%	$137.4623	$137.46	$137.45	$137.50
Purchase #2	$227.96	11.356%	$253.8471	$253.85	$253.85	$253.80
Purchase #3	$186.48	5.468%	$196.6767	$196.68	$196.70	$196.70
Purchase #4	$73.48	9.520%	$80.4753	$80.48	$80.50	$80.50
Purchase #5	$138.64	9.241%	$151.4517	$151.45	$151.45	$151.50
Purchase #6	$228.88	5.389%	$241.2143	$241.21	$241.20	$241.20
Purchase #7	$57.28	7.389%	$61.5124	$61.51	$61.50	$61.50
7 purchase totals =	$1,040.39		$1,122.6398	$1,122.64	$1,122.65	$1,122.70