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	$175.64	11.738%	$196.2566	$196.26	$196.25	$196.30
Purchase #2	$131.31	7.784%	$141.5312	$141.53	$141.55	$141.50
Purchase #3	$18.79	5.259%	$19.7782	$19.78	$19.80	$19.80
Purchase #4	$85.85	13.791%	$97.6896	$97.69	$97.70	$97.70
Purchase #5	$125.35	8.807%	$136.3896	$136.39	$136.40	$136.40
Purchase #6	$31.43	11.845%	$35.1529	$35.15	$35.15	$35.20
Purchase #7	$92.46	11.807%	$103.3768	$103.38	$103.40	$103.40
7 purchase totals =	$660.83		$730.1749	$730.18	$730.25	$730.30