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	$100.62	10.215%	$110.8983	$110.90	$110.90	$110.90
Purchase #2	$16.31	13.506%	$18.5128	$18.51	$18.50	$18.50
Purchase #3	$11.47	10.481%	$12.6722	$12.67	$12.65	$12.70
Purchase #4	$204.59	5.651%	$216.1514	$216.15	$216.15	$216.20
Purchase #5	$160.28	13.564%	$182.0204	$182.02	$182.00	$182.00
Purchase #6	$178.78	9.863%	$196.4131	$196.41	$196.40	$196.40
Purchase #7	$52.37	8.481%	$56.8115	$56.81	$56.80	$56.80
7 purchase totals =	$724.42		$793.4797	$793.47	$793.40	$793.50