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	$43.38	5.246%	$45.6557	$45.66	$45.65	$45.70
Purchase #2	$47.28	13.216%	$53.5285	$53.53	$53.55	$53.50
Purchase #3	$144.48	8.465%	$156.7102	$156.71	$156.70	$156.70
Purchase #4	$242.64	7.584%	$261.0418	$261.04	$261.05	$261.00
Purchase #5	$81.82	10.406%	$90.3342	$90.33	$90.35	$90.30
Purchase #6	$194.60	10.736%	$215.4923	$215.49	$215.50	$215.50
Purchase #7	$84.53	11.869%	$94.5629	$94.56	$94.55	$94.60
7 purchase totals =	$838.73		$917.3256	$917.32	$917.35	$917.30