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	$99.63	7.345%	$106.9478	$106.95	$106.95	$106.90
Purchase #2	$113.74	5.118%	$119.5612	$119.56	$119.55	$119.60
Purchase #3	$69.81	11.578%	$77.8926	$77.89	$77.90	$77.90
Purchase #4	$92.81	11.620%	$103.5945	$103.59	$103.60	$103.60
Purchase #5	$221.60	8.505%	$240.4471	$240.45	$240.45	$240.40
Purchase #6	$150.72	6.564%	$160.6133	$160.61	$160.60	$160.60
Purchase #7	$172.74	4.182%	$179.964	$179.96	$179.95	$180.00
7 purchase totals =	$921.05		$989.0205	$989.01	$989.00	$989.00