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	$29.46	10.132%	$32.4449	$32.44	$32.45	$32.40
Purchase #2	$140.93	3.343%	$145.6413	$145.64	$145.65	$145.60
Purchase #3	$62.86	5.490%	$66.311	$66.31	$66.30	$66.30
Purchase #4	$104.43	7.648%	$112.4168	$112.42	$112.40	$112.40
Purchase #5	$172.83	11.472%	$192.6571	$192.66	$192.65	$192.70
Purchase #6	$189.87	12.619%	$213.8297	$213.83	$213.85	$213.80
Purchase #7	$248.76	6.463%	$264.8374	$264.84	$264.85	$264.80
7 purchase totals =	$949.14		$1,028.1382	$1,028.14	$1,028.15	$1,028.00