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	$102.94	9.754%	$112.9808	$112.98	$113.00	$113.00
Purchase #2	$78.54	13.811%	$89.3872	$89.39	$89.40	$89.40
Purchase #3	$170.46	10.655%	$188.6225	$188.62	$188.60	$188.60
Purchase #4	$155.31	8.264%	$168.1448	$168.14	$168.15	$168.10
Purchase #5	$221.59	6.402%	$235.7762	$235.78	$235.80	$235.80
Purchase #6	$6.93	13.454%	$7.8624	$7.86	$7.85	$7.90
Purchase #7	$224.89	13.402%	$255.0298	$255.03	$255.05	$255.00
7 purchase totals =	$960.66		$1,057.8037	$1,057.80	$1,057.85	$1,057.80