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	$142.59	12.375%	$160.2355	$160.24	$160.25	$160.20
Purchase #2	$165.35	11.291%	$184.0197	$184.02	$184.00	$184.00
Purchase #3	$34.25	4.837%	$35.9067	$35.91	$35.90	$35.90
Purchase #4	$102.62	6.678%	$109.473	$109.47	$109.45	$109.50
Purchase #5	$89.39	12.865%	$100.89	$100.89	$100.90	$100.90
Purchase #6	$8.30	6.694%	$8.8556	$8.86	$8.85	$8.90
Purchase #7	$215.29	10.146%	$237.1333	$237.13	$237.15	$237.10
7 purchase totals =	$757.79		$836.5138	$836.52	$836.50	$836.50