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	$238.25	10.295%	$262.7778	$262.78	$262.80	$262.80
Purchase #2	$235.58	10.474%	$260.2546	$260.25	$260.25	$260.30
Purchase #3	$181.98	7.120%	$194.937	$194.94	$194.95	$194.90
Purchase #4	$62.74	3.464%	$64.9133	$64.91	$64.90	$64.90
Purchase #5	$125.73	8.599%	$136.5415	$136.54	$136.55	$136.50
Purchase #6	$45.92	10.752%	$50.8573	$50.86	$50.85	$50.90
Purchase #7	$164.49	12.792%	$185.5316	$185.53	$185.55	$185.50
7 purchase totals =	$1,054.69		$1,155.8131	$1,155.81	$1,155.85	$1,155.80