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	$229.69	11.305%	$255.6565	$255.66	$255.65	$255.70
Purchase #2	$136.35	12.464%	$153.3447	$153.34	$153.35	$153.30
Purchase #3	$34.40	7.591%	$37.0113	$37.01	$37.00	$37.00
Purchase #4	$238.68	7.624%	$256.877	$256.88	$256.90	$256.90
Purchase #5	$124.41	4.698%	$130.2548	$130.25	$130.25	$130.30
Purchase #6	$27.43	4.151%	$28.5686	$28.57	$28.55	$28.60
Purchase #7	$99.31	10.319%	$109.5578	$109.56	$109.55	$109.60
7 purchase totals =	$890.27		$971.2707	$971.27	$971.25	$971.40