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	$176.35	11.664%	$196.9195	$196.92	$196.90	$196.90
Purchase #2	$40.47	11.192%	$44.9994	$45.00	$45.00	$45.00
Purchase #3	$104.67	7.441%	$112.4585	$112.46	$112.45	$112.50
Purchase #4	$110.80	7.762%	$119.4003	$119.40	$119.40	$119.40
Purchase #5	$213.44	13.584%	$242.4337	$242.43	$242.45	$242.40
Purchase #6	$138.33	12.566%	$155.7125	$155.71	$155.70	$155.70
Purchase #7	$34.28	7.651%	$36.9028	$36.90	$36.90	$36.90
7 purchase totals =	$818.34		$908.8267	$908.82	$908.80	$908.80