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	$214.46	13.688%	$243.8153	$243.82	$243.80	$243.80
Purchase #2	$225.44	10.864%	$249.9318	$249.93	$249.95	$249.90
Purchase #3	$64.96	13.690%	$73.853	$73.85	$73.85	$73.90
Purchase #4	$142.71	5.504%	$150.5648	$150.56	$150.55	$150.60
Purchase #5	$94.33	4.473%	$98.5494	$98.55	$98.55	$98.50
Purchase #6	$229.56	8.540%	$249.1644	$249.16	$249.15	$249.20
Purchase #7	$44.70	13.653%	$50.8029	$50.80	$50.80	$50.80
7 purchase totals =	$1,016.16		$1,116.6816	$1,116.67	$1,116.65	$1,116.70