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	$187.60	7.107%	$200.9327	$200.93	$200.95	$200.90
Purchase #2	$91.48	4.468%	$95.5673	$95.57	$95.55	$95.60
Purchase #3	$214.91	4.133%	$223.7922	$223.79	$223.80	$223.80
Purchase #4	$61.38	11.871%	$68.6664	$68.67	$68.65	$68.70
Purchase #5	$52.76	13.537%	$59.9021	$59.90	$59.90	$59.90
Purchase #6	$219.67	5.324%	$231.3652	$231.37	$231.35	$231.40
Purchase #7	$32.56	9.399%	$35.6203	$35.62	$35.60	$35.60
7 purchase totals =	$860.36		$915.8462	$915.85	$915.80	$915.90