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	$81.60	4.747%	$85.4736	$85.47	$85.45	$85.50
Purchase #2	$35.62	4.158%	$37.1011	$37.10	$37.10	$37.10
Purchase #3	$184.67	3.379%	$190.91	$190.91	$190.90	$190.90
Purchase #4	$14.39	6.144%	$15.2741	$15.27	$15.25	$15.30
Purchase #5	$78.48	6.217%	$83.3591	$83.36	$83.35	$83.40
Purchase #6	$69.77	7.316%	$74.8744	$74.87	$74.85	$74.90
Purchase #7	$35.52	4.295%	$37.0456	$37.05	$37.05	$37.00
7 purchase totals =	$500.05		$524.0379	$524.03	$523.95	$524.10