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	$63.78	3.349%	$65.916	$65.92	$65.90	$65.90
Purchase #2	$6.84	8.198%	$7.4007	$7.40	$7.40	$7.40
Purchase #3	$15.73	12.505%	$17.697	$17.70	$17.70	$17.70
Purchase #4	$216.69	3.608%	$224.5082	$224.51	$224.50	$224.50
Purchase #5	$157.42	4.742%	$164.8849	$164.88	$164.90	$164.90
Purchase #6	$10.85	4.663%	$11.3559	$11.36	$11.35	$11.40
Purchase #7	$38.37	12.759%	$43.2656	$43.27	$43.25	$43.30
7 purchase totals =	$509.68		$535.0283	$535.04	$535.00	$535.10