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	$131.25	7.354%	$140.9021	$140.90	$140.90	$140.90
Purchase #2	$229.87	13.742%	$261.4587	$261.46	$261.45	$261.50
Purchase #3	$66.69	6.277%	$70.8761	$70.88	$70.90	$70.90
Purchase #4	$200.64	8.530%	$217.7546	$217.75	$217.75	$217.80
Purchase #5	$246.47	9.859%	$270.7695	$270.77	$270.75	$270.80
Purchase #6	$55.95	6.708%	$59.7031	$59.70	$59.70	$59.70
Purchase #7	$109.71	13.521%	$124.5439	$124.54	$124.55	$124.50
7 purchase totals =	$1,040.58		$1,146.0080	$1,146.00	$1,146.00	$1,146.10