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	$134.35	6.800%	$143.4858	$143.49	$143.50	$143.50
Purchase #2	$200.65	6.583%	$213.8588	$213.86	$213.85	$213.90
Purchase #3	$64.66	8.838%	$70.3747	$70.37	$70.35	$70.40
Purchase #4	$102.67	6.776%	$109.6269	$109.63	$109.65	$109.60
Purchase #5	$85.31	6.712%	$91.036	$91.04	$91.05	$91.00
Purchase #6	$67.72	6.422%	$72.069	$72.07	$72.05	$72.10
Purchase #7	$12.58	7.392%	$13.5099	$13.51	$13.50	$13.50
7 purchase totals =	$667.94		$713.9611	$713.97	$713.95	$714.00