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	$196.90	6.838%	$210.364	$210.36	$210.35	$210.40
Purchase #2	$29.89	5.134%	$31.4246	$31.42	$31.40	$31.40
Purchase #3	$87.41	13.339%	$99.0696	$99.07	$99.05	$99.10
Purchase #4	$138.49	5.736%	$146.4338	$146.43	$146.45	$146.40
Purchase #5	$239.77	9.293%	$262.0518	$262.05	$262.05	$262.10
Purchase #6	$85.70	9.611%	$93.9366	$93.94	$93.95	$93.90
Purchase #7	$74.48	10.811%	$82.532	$82.53	$82.55	$82.50
7 purchase totals =	$852.64		$925.8124	$925.80	$925.80	$925.80