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	$173.73	13.274%	$196.7909	$196.79	$196.80	$196.80
Purchase #2	$170.52	5.599%	$180.0674	$180.07	$180.05	$180.10
Purchase #3	$237.89	3.785%	$246.8941	$246.89	$246.90	$246.90
Purchase #4	$150.70	10.325%	$166.2598	$166.26	$166.25	$166.30
Purchase #5	$119.61	6.349%	$127.204	$127.20	$127.20	$127.20
Purchase #6	$6.88	3.610%	$7.1284	$7.13	$7.15	$7.10
Purchase #7	$208.96	3.631%	$216.5473	$216.55	$216.55	$216.50
7 purchase totals =	$1,068.29		$1,140.8919	$1,140.89	$1,140.90	$1,140.90