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	$99.50	12.270%	$111.7087	$111.71	$111.70	$111.70
Purchase #2	$183.44	11.208%	$204	$204.00	$204.00	$204.00
Purchase #3	$205.39	8.846%	$223.5588	$223.56	$223.55	$223.60
Purchase #4	$195.89	5.567%	$206.7952	$206.80	$206.80	$206.80
Purchase #5	$131.89	9.106%	$143.8999	$143.90	$143.90	$143.90
Purchase #6	$138.25	13.254%	$156.5737	$156.57	$156.55	$156.60
Purchase #7	$9.92	4.797%	$10.3959	$10.40	$10.40	$10.40
7 purchase totals =	$964.28		$1,056.9322	$1,056.94	$1,056.90	$1,057.00