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	$77.91	5.194%	$81.9566	$81.96	$81.95	$82.00
Purchase #2	$87.75	4.545%	$91.7382	$91.74	$91.75	$91.70
Purchase #3	$11.48	9.674%	$12.5906	$12.59	$12.60	$12.60
Purchase #4	$35.95	12.577%	$40.4714	$40.47	$40.45	$40.50
Purchase #5	$133.96	10.386%	$147.8731	$147.87	$147.85	$147.90
Purchase #6	$52.42	7.695%	$56.4537	$56.45	$56.45	$56.50
Purchase #7	$94.83	4.356%	$98.9608	$98.96	$98.95	$99.00
7 purchase totals =	$494.30		$530.0444	$530.04	$530.00	$530.20