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	$108.72	13.588%	$123.4929	$123.49	$123.50	$123.50
Purchase #2	$68.55	4.268%	$71.4757	$71.48	$71.50	$71.50
Purchase #3	$171.89	8.586%	$186.6485	$186.65	$186.65	$186.60
Purchase #4	$97.65	6.233%	$103.7365	$103.74	$103.75	$103.70
Purchase #5	$70.48	4.353%	$73.548	$73.55	$73.55	$73.50
Purchase #6	$6.71	6.629%	$7.1548	$7.15	$7.15	$7.20
Purchase #7	$190.45	6.143%	$202.1493	$202.15	$202.15	$202.10
7 purchase totals =	$714.45		$768.2057	$768.21	$768.25	$768.10