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	$229.64	5.666%	$242.6514	$242.65	$242.65	$242.70
Purchase #2	$73.36	11.740%	$81.9725	$81.97	$81.95	$82.00
Purchase #3	$38.31	5.604%	$40.4569	$40.46	$40.45	$40.50
Purchase #4	$164.38	3.328%	$169.8506	$169.85	$169.85	$169.90
Purchase #5	$208.59	12.405%	$234.4656	$234.47	$234.45	$234.50
Purchase #6	$90.63	10.806%	$100.4235	$100.42	$100.40	$100.40
Purchase #7	$136.86	4.111%	$142.4863	$142.49	$142.50	$142.50
7 purchase totals =	$941.77		$1,012.3068	$1,012.31	$1,012.25	$1,012.50