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	$180.49	5.762%	$190.8898	$190.89	$190.90	$190.90
Purchase #2	$101.83	12.397%	$114.4539	$114.45	$114.45	$114.50
Purchase #3	$99.94	3.845%	$103.7827	$103.78	$103.80	$103.80
Purchase #4	$217.29	13.642%	$246.9327	$246.93	$246.95	$246.90
Purchase #5	$205.88	5.311%	$216.8143	$216.81	$216.80	$216.80
Purchase #6	$180.84	5.213%	$190.2672	$190.27	$190.25	$190.30
Purchase #7	$215.60	11.564%	$240.532	$240.53	$240.55	$240.50
7 purchase totals =	$1,201.87		$1,303.6726	$1,303.66	$1,303.70	$1,303.70