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	$203.34	9.475%	$222.6065	$222.61	$222.60	$222.60
Purchase #2	$31.85	5.696%	$33.6642	$33.66	$33.65	$33.70
Purchase #3	$175.72	4.528%	$183.6766	$183.68	$183.70	$183.70
Purchase #4	$72.74	4.789%	$76.2235	$76.22	$76.20	$76.20
Purchase #5	$110.47	7.511%	$118.7674	$118.77	$118.75	$118.80
Purchase #6	$229.73	12.704%	$258.9149	$258.91	$258.90	$258.90
Purchase #7	$215.83	6.536%	$229.9366	$229.94	$229.95	$229.90
7 purchase totals =	$1,039.68		$1,123.7897	$1,123.79	$1,123.75	$1,123.80