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	$123.94	5.796%	$131.1236	$131.12	$131.10	$131.10
Purchase #2	$126.83	6.443%	$135.0017	$135.00	$135.00	$135.00
Purchase #3	$187.38	7.433%	$201.308	$201.31	$201.30	$201.30
Purchase #4	$226.55	13.434%	$256.9847	$256.98	$257.00	$257.00
Purchase #5	$142.93	10.181%	$157.4817	$157.48	$157.50	$157.50
Purchase #6	$118.94	10.506%	$131.4358	$131.44	$131.45	$131.40
Purchase #7	$93.77	4.308%	$97.8096	$97.81	$97.80	$97.80
7 purchase totals =	$1,020.34		$1,111.1451	$1,111.14	$1,111.15	$1,111.10