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	$67.42	7.810%	$72.6855	$72.69	$72.70	$72.70
Purchase #2	$217.38	4.670%	$227.5316	$227.53	$227.55	$227.50
Purchase #3	$197.79	11.221%	$219.984	$219.98	$220.00	$220.00
Purchase #4	$94.58	4.236%	$98.5864	$98.59	$98.60	$98.60
Purchase #5	$234.32	6.769%	$250.1811	$250.18	$250.20	$250.20
Purchase #6	$29.56	7.792%	$31.8633	$31.86	$31.85	$31.90
Purchase #7	$94.58	6.518%	$100.7447	$100.74	$100.75	$100.70
7 purchase totals =	$935.63		$1,001.5766	$1,001.57	$1,001.65	$1,001.60