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	$82.39	3.273%	$85.0866	$85.09	$85.10	$85.10
Purchase #2	$193.44	8.381%	$209.6522	$209.65	$209.65	$209.70
Purchase #3	$36.45	6.696%	$38.8907	$38.89	$38.90	$38.90
Purchase #4	$246.75	9.631%	$270.5145	$270.51	$270.50	$270.50
Purchase #5	$84.64	7.142%	$90.685	$90.69	$90.70	$90.70
Purchase #6	$116.85	4.349%	$121.9318	$121.93	$121.95	$121.90
Purchase #7	$177.71	7.712%	$191.415	$191.42	$191.40	$191.40
7 purchase totals =	$938.23		$1,008.1758	$1,008.18	$1,008.20	$1,008.20