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	$192.93	10.134%	$212.4815	$212.48	$212.50	$212.50
Purchase #2	$94.45	10.449%	$104.3191	$104.32	$104.30	$104.30
Purchase #3	$98.28	7.355%	$105.5085	$105.51	$105.50	$105.50
Purchase #4	$167.66	4.593%	$175.3606	$175.36	$175.35	$175.40
Purchase #5	$51.66	7.859%	$55.72	$55.72	$55.70	$55.70
Purchase #6	$31.49	12.376%	$35.3872	$35.39	$35.40	$35.40
Purchase #7	$126.50	8.675%	$137.4739	$137.47	$137.45	$137.50
7 purchase totals =	$762.97		$826.2508	$826.25	$826.20	$826.30