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	$114.76	4.447%	$119.8634	$119.86	$119.85	$119.90
Purchase #2	$33.89	10.659%	$37.5023	$37.50	$37.50	$37.50
Purchase #3	$119.57	6.402%	$127.2249	$127.22	$127.20	$127.20
Purchase #4	$173.79	6.403%	$184.9178	$184.92	$184.90	$184.90
Purchase #5	$10.25	5.608%	$10.8248	$10.82	$10.80	$10.80
Purchase #6	$175.25	13.838%	$199.5011	$199.50	$199.50	$199.50
Purchase #7	$28.67	8.509%	$31.1095	$31.11	$31.10	$31.10
7 purchase totals =	$656.18		$710.9438	$710.93	$710.85	$710.90