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	$148.31	13.674%	$168.5899	$168.59	$168.60	$168.60
Purchase #2	$171.91	8.765%	$186.9779	$186.98	$187.00	$187.00
Purchase #3	$99.85	13.803%	$113.6323	$113.63	$113.65	$113.60
Purchase #4	$102.86	6.434%	$109.478	$109.48	$109.50	$109.50
Purchase #5	$183.87	3.449%	$190.2117	$190.21	$190.20	$190.20
Purchase #6	$78.48	8.622%	$85.2465	$85.25	$85.25	$85.20
Purchase #7	$35.93	6.745%	$38.3535	$38.35	$38.35	$38.40
7 purchase totals =	$821.21		$892.4898	$892.49	$892.55	$892.50