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	$192.55	12.851%	$217.2946	$217.29	$217.30	$217.30
Purchase #2	$67.69	5.648%	$71.5131	$71.51	$71.50	$71.50
Purchase #3	$168.51	12.240%	$189.1356	$189.14	$189.15	$189.10
Purchase #4	$153.39	10.577%	$169.6141	$169.61	$169.60	$169.60
Purchase #5	$32.46	6.658%	$34.6212	$34.62	$34.60	$34.60
Purchase #6	$76.53	11.549%	$85.3684	$85.37	$85.35	$85.40
Purchase #7	$215.42	6.314%	$229.0216	$229.02	$229.00	$229.00
7 purchase totals =	$906.55		$996.5686	$996.56	$996.50	$996.50