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	$204.76	4.282%	$213.5278	$213.53	$213.55	$213.50
Purchase #2	$218.87	4.176%	$228.01	$228.01	$228.00	$228.00
Purchase #3	$66.90	6.395%	$71.1783	$71.18	$71.20	$71.20
Purchase #4	$82.75	8.614%	$89.8781	$89.88	$89.90	$89.90
Purchase #5	$33.71	13.452%	$38.2447	$38.24	$38.25	$38.20
Purchase #6	$152.33	3.292%	$157.3447	$157.34	$157.35	$157.30
Purchase #7	$90.86	13.725%	$103.3305	$103.33	$103.35	$103.30
7 purchase totals =	$850.18		$901.5141	$901.51	$901.60	$901.40