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	$30.73	7.195%	$32.941	$32.94	$32.95	$32.90
Purchase #2	$54.47	5.127%	$57.2627	$57.26	$57.25	$57.30
Purchase #3	$140.93	6.779%	$150.4836	$150.48	$150.50	$150.50
Purchase #4	$52.62	4.119%	$54.7874	$54.79	$54.80	$54.80
Purchase #5	$107.82	11.721%	$120.4576	$120.46	$120.45	$120.50
Purchase #6	$19.54	12.139%	$21.912	$21.91	$21.90	$21.90
Purchase #7	$198.45	5.238%	$208.8448	$208.84	$208.85	$208.80
7 purchase totals =	$604.56		$646.6891	$646.68	$646.70	$646.70