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	$232.90	12.727%	$262.5412	$262.54	$262.55	$262.50
Purchase #2	$183.42	13.665%	$208.4843	$208.48	$208.50	$208.50
Purchase #3	$21.40	6.273%	$22.7424	$22.74	$22.75	$22.70
Purchase #4	$81.27	11.706%	$90.7835	$90.78	$90.80	$90.80
Purchase #5	$168.43	3.764%	$174.7697	$174.77	$174.75	$174.80
Purchase #6	$237.77	13.529%	$269.9379	$269.94	$269.95	$269.90
Purchase #7	$6.77	6.458%	$7.2072	$7.21	$7.20	$7.20
7 purchase totals =	$931.96		$1,036.4662	$1,036.46	$1,036.50	$1,036.40