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	$65.50	7.285%	$70.2717	$70.27	$70.25	$70.30
Purchase #2	$209.87	8.328%	$227.348	$227.35	$227.35	$227.30
Purchase #3	$66.94	8.614%	$72.7062	$72.71	$72.70	$72.70
Purchase #4	$168.48	7.329%	$180.8279	$180.83	$180.85	$180.80
Purchase #5	$50.59	6.506%	$53.8814	$53.88	$53.90	$53.90
Purchase #6	$181.36	5.128%	$190.6601	$190.66	$190.65	$190.70
Purchase #7	$201.57	7.247%	$216.1778	$216.18	$216.20	$216.20
7 purchase totals =	$944.31		$1,011.8731	$1,011.88	$1,011.90	$1,011.90