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	$40.83	10.492%	$45.1139	$45.11	$45.10	$45.10
Purchase #2	$198.88	8.241%	$215.2697	$215.27	$215.25	$215.30
Purchase #3	$246.57	3.579%	$255.3947	$255.39	$255.40	$255.40
Purchase #4	$164.67	10.147%	$181.3791	$181.38	$181.40	$181.40
Purchase #5	$11.31	10.307%	$12.4757	$12.48	$12.50	$12.50
Purchase #6	$75.30	3.344%	$77.818	$77.82	$77.80	$77.80
Purchase #7	$88.54	6.156%	$93.9905	$93.99	$94.00	$94.00
7 purchase totals =	$826.10		$881.4416	$881.44	$881.45	$881.50