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	$228.70	11.839%	$255.7758	$255.78	$255.80	$255.80
Purchase #2	$78.43	13.676%	$89.1561	$89.16	$89.15	$89.20
Purchase #3	$79.89	7.660%	$86.0096	$86.01	$86.00	$86.00
Purchase #4	$110.83	6.504%	$118.0384	$118.04	$118.05	$118.00
Purchase #5	$169.87	7.325%	$182.313	$182.31	$182.30	$182.30
Purchase #6	$152.27	5.725%	$160.9875	$160.99	$161.00	$161.00
Purchase #7	$216.58	11.172%	$240.7763	$240.78	$240.80	$240.80
7 purchase totals =	$1,036.57		$1,133.0567	$1,133.07	$1,133.10	$1,133.10