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	$151.75	11.194%	$168.7369	$168.74	$168.75	$168.70
Purchase #2	$98.79	8.757%	$107.441	$107.44	$107.45	$107.40
Purchase #3	$111.34	13.491%	$126.3609	$126.36	$126.35	$126.40
Purchase #4	$90.71	3.638%	$94.01	$94.01	$94.00	$94.00
Purchase #5	$215.91	11.499%	$240.7375	$240.74	$240.75	$240.70
Purchase #6	$169.62	12.275%	$190.4409	$190.44	$190.45	$190.40
Purchase #7	$84.74	7.227%	$90.8642	$90.86	$90.85	$90.90
7 purchase totals =	$922.86		$1,018.5914	$1,018.59	$1,018.60	$1,018.50