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	$186.47	7.492%	$200.4403	$200.44	$200.45	$200.40
Purchase #2	$113.37	5.160%	$119.2199	$119.22	$119.20	$119.20
Purchase #3	$234.26	3.244%	$241.8594	$241.86	$241.85	$241.90
Purchase #4	$224.57	10.359%	$247.8332	$247.83	$247.85	$247.80
Purchase #5	$105.53	5.715%	$111.561	$111.56	$111.55	$111.60
Purchase #6	$174.93	3.166%	$180.4683	$180.47	$180.45	$180.50
Purchase #7	$29.57	3.279%	$30.5396	$30.54	$30.55	$30.50
7 purchase totals =	$1,068.70		$1,131.9217	$1,131.92	$1,131.90	$1,131.90