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	$101.94	10.712%	$112.8598	$112.86	$112.85	$112.90
Purchase #2	$160.56	7.667%	$172.8701	$172.87	$172.85	$172.90
Purchase #3	$234.60	8.490%	$254.5175	$254.52	$254.50	$254.50
Purchase #4	$74.61	10.762%	$82.6395	$82.64	$82.65	$82.60
Purchase #5	$7.63	8.192%	$8.255	$8.26	$8.25	$8.30
Purchase #6	$99.30	6.422%	$105.677	$105.68	$105.70	$105.70
Purchase #7	$88.86	10.861%	$98.5111	$98.51	$98.50	$98.50
7 purchase totals =	$767.50		$835.3300	$835.34	$835.30	$835.40