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	$181.93	10.172%	$200.4359	$200.44	$200.45	$200.40
Purchase #2	$137.89	11.572%	$153.8466	$153.85	$153.85	$153.80
Purchase #3	$72.34	6.253%	$76.8634	$76.86	$76.85	$76.90
Purchase #4	$196.67	6.189%	$208.8419	$208.84	$208.85	$208.80
Purchase #5	$116.73	12.639%	$131.4835	$131.48	$131.50	$131.50
Purchase #6	$222.69	12.506%	$250.5396	$250.54	$250.55	$250.50
Purchase #7	$188.41	8.542%	$204.504	$204.50	$204.50	$204.50
7 purchase totals =	$1,116.66		$1,226.5149	$1,226.51	$1,226.55	$1,226.40