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	$101.69	3.675%	$105.4271	$105.43	$105.45	$105.40
Purchase #2	$223.94	12.296%	$251.4757	$251.48	$251.50	$251.50
Purchase #3	$29.69	4.385%	$30.9919	$30.99	$31.00	$31.00
Purchase #4	$208.70	5.165%	$219.4794	$219.48	$219.50	$219.50
Purchase #5	$232.94	4.221%	$242.7724	$242.77	$242.75	$242.80
Purchase #6	$63.68	13.667%	$72.3831	$72.38	$72.40	$72.40
Purchase #7	$44.67	4.868%	$46.8445	$46.84	$46.85	$46.80
7 purchase totals =	$905.31		$969.3741	$969.37	$969.45	$969.40