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	$35.48	6.171%	$37.6695	$37.67	$37.65	$37.70
Purchase #2	$10.65	10.842%	$11.8047	$11.80	$11.80	$11.80
Purchase #3	$239.71	13.841%	$272.8883	$272.89	$272.90	$272.90
Purchase #4	$139.32	4.340%	$145.3665	$145.37	$145.35	$145.40
Purchase #5	$13.69	10.141%	$15.0783	$15.08	$15.10	$15.10
Purchase #6	$246.91	6.220%	$262.2678	$262.27	$262.25	$262.30
Purchase #7	$246.77	10.313%	$272.2194	$272.22	$272.20	$272.20
7 purchase totals =	$932.53		$1,017.2945	$1,017.30	$1,017.25	$1,017.40