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	$45.58	5.200%	$47.9502	$47.95	$47.95	$48.00
Purchase #2	$52.34	4.557%	$54.7251	$54.73	$54.75	$54.70
Purchase #3	$222.46	3.803%	$230.9202	$230.92	$230.90	$230.90
Purchase #4	$203.59	8.411%	$220.714	$220.71	$220.70	$220.70
Purchase #5	$179.27	6.815%	$191.4873	$191.49	$191.50	$191.50
Purchase #6	$164.50	11.578%	$183.5458	$183.55	$183.55	$183.50
Purchase #7	$139.73	8.151%	$151.1194	$151.12	$151.10	$151.10
7 purchase totals =	$1,007.47		$1,080.4620	$1,080.47	$1,080.45	$1,080.40