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	$31.57	5.549%	$33.3218	$33.32	$33.30	$33.30
Purchase #2	$142.47	5.654%	$150.5253	$150.53	$150.55	$150.50
Purchase #3	$155.38	11.816%	$173.7397	$173.74	$173.75	$173.70
Purchase #4	$136.41	5.164%	$143.4542	$143.45	$143.45	$143.50
Purchase #5	$213.59	10.527%	$236.0746	$236.07	$236.05	$236.10
Purchase #6	$80.83	6.569%	$86.1397	$86.14	$86.15	$86.10
Purchase #7	$133.33	6.469%	$141.9551	$141.96	$141.95	$142.00
7 purchase totals =	$893.58		$965.2104	$965.21	$965.20	$965.20