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	$30.83	12.151%	$34.5762	$34.58	$34.60	$34.60
Purchase #2	$167.57	7.178%	$179.5982	$179.60	$179.60	$179.60
Purchase #3	$105.80	7.647%	$113.8905	$113.89	$113.90	$113.90
Purchase #4	$213.32	6.464%	$227.109	$227.11	$227.10	$227.10
Purchase #5	$139.57	12.281%	$156.7106	$156.71	$156.70	$156.70
Purchase #6	$180.34	4.270%	$188.0405	$188.04	$188.05	$188.00
Purchase #7	$227.57	11.732%	$254.2685	$254.27	$254.25	$254.30
7 purchase totals =	$1,065.00		$1,154.1935	$1,154.20	$1,154.20	$1,154.20