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	$40.88	8.515%	$44.3609	$44.36	$44.35	$44.40
Purchase #2	$198.67	3.728%	$206.0764	$206.08	$206.10	$206.10
Purchase #3	$201.84	11.418%	$224.8861	$224.89	$224.90	$224.90
Purchase #4	$9.68	9.727%	$10.6216	$10.62	$10.60	$10.60
Purchase #5	$123.86	11.820%	$138.5003	$138.50	$138.50	$138.50
Purchase #6	$123.55	6.310%	$131.346	$131.35	$131.35	$131.30
Purchase #7	$70.76	11.250%	$78.7205	$78.72	$78.70	$78.70
7 purchase totals =	$769.24		$834.5118	$834.52	$834.50	$834.50