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	$243.74	10.559%	$269.4765	$269.48	$269.50	$269.50
Purchase #2	$84.28	13.298%	$95.4876	$95.49	$95.50	$95.50
Purchase #3	$72.64	8.489%	$78.8064	$78.81	$78.80	$78.80
Purchase #4	$208.99	7.447%	$224.5535	$224.55	$224.55	$224.60
Purchase #5	$166.65	8.151%	$180.2336	$180.23	$180.25	$180.20
Purchase #6	$16.69	11.410%	$18.5943	$18.59	$18.60	$18.60
Purchase #7	$140.48	10.491%	$155.2178	$155.22	$155.20	$155.20
7 purchase totals =	$933.47		$1,022.3697	$1,022.37	$1,022.40	$1,022.40