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	$215.51	10.578%	$238.3066	$238.31	$238.30	$238.30
Purchase #2	$127.55	12.642%	$143.6749	$143.67	$143.65	$143.70
Purchase #3	$130.54	7.793%	$140.713	$140.71	$140.70	$140.70
Purchase #4	$79.48	7.464%	$85.4124	$85.41	$85.40	$85.40
Purchase #5	$113.84	3.322%	$117.6218	$117.62	$117.60	$117.60
Purchase #6	$157.89	5.572%	$166.6876	$166.69	$166.70	$166.70
Purchase #7	$141.43	12.273%	$158.7877	$158.79	$158.80	$158.80
7 purchase totals =	$966.24		$1,051.2040	$1,051.20	$1,051.15	$1,051.20