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	$166.94	3.348%	$172.5292	$172.53	$172.55	$172.50
Purchase #2	$222.33	7.862%	$239.8096	$239.81	$239.80	$239.80
Purchase #3	$6.60	5.443%	$6.9592	$6.96	$6.95	$7.00
Purchase #4	$213.73	4.427%	$223.1918	$223.19	$223.20	$223.20
Purchase #5	$118.29	13.659%	$134.4472	$134.45	$134.45	$134.40
Purchase #6	$29.57	7.378%	$31.7517	$31.75	$31.75	$31.80
Purchase #7	$206.89	11.118%	$229.892	$229.89	$229.90	$229.90
7 purchase totals =	$964.35		$1,038.5807	$1,038.58	$1,038.60	$1,038.60