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	$200.69	12.504%	$225.7843	$225.78	$225.80	$225.80
Purchase #2	$36.35	10.680%	$40.2322	$40.23	$40.25	$40.20
Purchase #3	$92.54	7.505%	$99.4851	$99.49	$99.50	$99.50
Purchase #4	$241.77	4.352%	$252.2918	$252.29	$252.30	$252.30
Purchase #5	$175.34	7.436%	$188.3783	$188.38	$188.40	$188.40
Purchase #6	$76.77	4.376%	$80.1295	$80.13	$80.15	$80.10
Purchase #7	$190.57	4.702%	$199.5306	$199.53	$199.55	$199.50
7 purchase totals =	$1,014.03		$1,085.8318	$1,085.83	$1,085.95	$1,085.80