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	$210.43	12.593%	$236.9294	$236.93	$236.95	$236.90
Purchase #2	$218.96	10.546%	$242.0515	$242.05	$242.05	$242.10
Purchase #3	$55.46	7.667%	$59.7121	$59.71	$59.70	$59.70
Purchase #4	$176.58	5.741%	$186.7175	$186.72	$186.70	$186.70
Purchase #5	$233.94	12.645%	$263.5217	$263.52	$263.50	$263.50
Purchase #6	$86.79	3.491%	$89.8198	$89.82	$89.80	$89.80
Purchase #7	$73.80	5.528%	$77.8797	$77.88	$77.90	$77.90
7 purchase totals =	$1,055.96		$1,156.6317	$1,156.63	$1,156.60	$1,156.60