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	$63.49	5.175%	$66.7756	$66.78	$66.80	$66.80
Purchase #2	$167.32	11.226%	$186.1033	$186.10	$186.10	$186.10
Purchase #3	$120.33	11.730%	$134.4447	$134.44	$134.45	$134.40
Purchase #4	$33.69	4.739%	$35.2866	$35.29	$35.30	$35.30
Purchase #5	$236.38	10.773%	$261.8452	$261.85	$261.85	$261.80
Purchase #6	$137.98	13.630%	$156.7867	$156.79	$156.80	$156.80
Purchase #7	$166.54	5.421%	$175.5681	$175.57	$175.55	$175.60
7 purchase totals =	$925.73		$1,016.8102	$1,016.82	$1,016.85	$1,016.80