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	$53.30	3.836%	$55.3446	$55.34	$55.35	$55.30
Purchase #2	$104.67	9.293%	$114.397	$114.40	$114.40	$114.40
Purchase #3	$121.69	9.700%	$133.4939	$133.49	$133.50	$133.50
Purchase #4	$168.29	7.366%	$180.6862	$180.69	$180.70	$180.70
Purchase #5	$13.71	7.833%	$14.7839	$14.78	$14.80	$14.80
Purchase #6	$53.84	7.542%	$57.9006	$57.90	$57.90	$57.90
Purchase #7	$172.96	4.573%	$180.8695	$180.87	$180.85	$180.90
7 purchase totals =	$688.46		$737.4757	$737.47	$737.50	$737.50