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	$46.73	3.256%	$48.2515	$48.25	$48.25	$48.30
Purchase #2	$55.45	13.380%	$62.8692	$62.87	$62.85	$62.90
Purchase #3	$48.59	13.449%	$55.1249	$55.12	$55.10	$55.10
Purchase #4	$86.26	5.372%	$90.8939	$90.89	$90.90	$90.90
Purchase #5	$182.91	10.376%	$201.8887	$201.89	$201.90	$201.90
Purchase #6	$176.92	11.259%	$196.8394	$196.84	$196.85	$196.80
Purchase #7	$155.43	5.442%	$163.8885	$163.89	$163.90	$163.90
7 purchase totals =	$752.29		$819.7561	$819.75	$819.75	$819.80