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	$81.71	3.383%	$84.4742	$84.47	$84.45	$84.50
Purchase #2	$197.94	11.151%	$220.0123	$220.01	$220.00	$220.00
Purchase #3	$218.83	4.244%	$228.1171	$228.12	$228.10	$228.10
Purchase #4	$185.38	8.213%	$200.6053	$200.61	$200.60	$200.60
Purchase #5	$169.91	12.416%	$191.006	$191.01	$191.00	$191.00
Purchase #6	$33.39	5.650%	$35.2765	$35.28	$35.30	$35.30
Purchase #7	$94.47	7.520%	$101.5741	$101.57	$101.55	$101.60
7 purchase totals =	$981.63		$1,061.0655	$1,061.07	$1,061.00	$1,061.10