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	$203.56	9.593%	$223.0875	$223.09	$223.10	$223.10
Purchase #2	$31.94	13.738%	$36.3279	$36.33	$36.35	$36.30
Purchase #3	$206.44	5.253%	$217.2843	$217.28	$217.30	$217.30
Purchase #4	$173.90	4.457%	$181.6507	$181.65	$181.65	$181.70
Purchase #5	$130.45	12.602%	$146.8893	$146.89	$146.90	$146.90
Purchase #6	$69.62	12.830%	$78.5522	$78.55	$78.55	$78.60
Purchase #7	$101.99	9.207%	$111.3802	$111.38	$111.40	$111.40
7 purchase totals =	$917.90		$995.1721	$995.17	$995.25	$995.30