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	$112.72	12.386%	$126.6815	$126.68	$126.70	$126.70
Purchase #2	$35.44	5.187%	$37.2783	$37.28	$37.30	$37.30
Purchase #3	$182.74	13.669%	$207.7187	$207.72	$207.70	$207.70
Purchase #4	$86.45	5.144%	$90.897	$90.90	$90.90	$90.90
Purchase #5	$94.87	10.449%	$104.783	$104.78	$104.80	$104.80
Purchase #6	$171.47	8.411%	$185.8923	$185.89	$185.90	$185.90
Purchase #7	$87.74	8.293%	$95.0163	$95.02	$95.00	$95.00
7 purchase totals =	$771.43		$848.2671	$848.27	$848.30	$848.30