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	$139.96	8.550%	$151.9266	$151.93	$151.95	$151.90
Purchase #2	$198.76	10.480%	$219.59	$219.59	$219.60	$219.60
Purchase #3	$218.96	10.729%	$242.4522	$242.45	$242.45	$242.50
Purchase #4	$20.78	8.153%	$22.4742	$22.47	$22.45	$22.50
Purchase #5	$35.51	3.583%	$36.7823	$36.78	$36.80	$36.80
Purchase #6	$54.29	9.323%	$59.3515	$59.35	$59.35	$59.40
Purchase #7	$189.86	3.136%	$195.814	$195.81	$195.80	$195.80
7 purchase totals =	$858.12		$928.3908	$928.38	$928.40	$928.50