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	$124.96	13.452%	$141.7696	$141.77	$141.75	$141.80
Purchase #2	$35.79	4.850%	$37.5258	$37.53	$37.55	$37.50
Purchase #3	$199.87	8.491%	$216.841	$216.84	$216.85	$216.80
Purchase #4	$11.48	4.830%	$12.0345	$12.03	$12.05	$12.00
Purchase #5	$79.29	5.314%	$83.5035	$83.50	$83.50	$83.50
Purchase #6	$135.42	3.729%	$140.4698	$140.47	$140.45	$140.50
Purchase #7	$94.35	6.392%	$100.3809	$100.38	$100.40	$100.40
7 purchase totals =	$681.16		$732.5251	$732.52	$732.55	$732.50