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	$67.49	6.796%	$72.0766	$72.08	$72.10	$72.10
Purchase #2	$231.78	10.640%	$256.4414	$256.44	$256.45	$256.40
Purchase #3	$52.88	4.549%	$55.2855	$55.29	$55.30	$55.30
Purchase #4	$234.78	5.233%	$247.066	$247.07	$247.05	$247.10
Purchase #5	$193.47	3.782%	$200.787	$200.79	$200.80	$200.80
Purchase #6	$191.48	13.630%	$217.5787	$217.58	$217.60	$217.60
Purchase #7	$203.66	7.785%	$219.5149	$219.51	$219.50	$219.50
7 purchase totals =	$1,175.54		$1,268.7501	$1,268.76	$1,268.80	$1,268.80