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	$202.47	9.437%	$221.5771	$221.58	$221.60	$221.60
Purchase #2	$95.74	11.546%	$106.7941	$106.79	$106.80	$106.80
Purchase #3	$10.53	6.743%	$11.24	$11.24	$11.25	$11.20
Purchase #4	$145.30	7.691%	$156.475	$156.48	$156.50	$156.50
Purchase #5	$238.34	10.282%	$262.8461	$262.85	$262.85	$262.80
Purchase #6	$233.50	9.162%	$254.8933	$254.89	$254.90	$254.90
Purchase #7	$61.66	7.478%	$66.2709	$66.27	$66.25	$66.30
7 purchase totals =	$987.54		$1,080.0965	$1,080.10	$1,080.15	$1,080.10