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	$110.99	7.155%	$118.9313	$118.93	$118.95	$118.90
Purchase #2	$59.74	3.801%	$62.0107	$62.01	$62.00	$62.00
Purchase #3	$29.25	9.380%	$31.9937	$31.99	$32.00	$32.00
Purchase #4	$39.81	10.308%	$43.9136	$43.91	$43.90	$43.90
Purchase #5	$229.59	11.185%	$255.2696	$255.27	$255.25	$255.30
Purchase #6	$246.28	10.829%	$272.9497	$272.95	$272.95	$272.90
Purchase #7	$57.71	4.795%	$60.4772	$60.48	$60.50	$60.50
7 purchase totals =	$773.37		$845.5458	$845.54	$845.55	$845.50