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	$105.63	3.386%	$109.2066	$109.21	$109.20	$109.20
Purchase #2	$147.53	5.377%	$155.4627	$155.46	$155.45	$155.50
Purchase #3	$31.33	7.615%	$33.7158	$33.72	$33.70	$33.70
Purchase #4	$81.78	8.176%	$88.4663	$88.47	$88.45	$88.50
Purchase #5	$203.97	9.319%	$222.978	$222.98	$223.00	$223.00
Purchase #6	$53.51	5.797%	$56.612	$56.61	$56.60	$56.60
Purchase #7	$105.63	13.184%	$119.5563	$119.56	$119.55	$119.60
7 purchase totals =	$729.38		$785.9977	$786.01	$785.95	$786.10