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	$11.93	9.115%	$13.0174	$13.02	$13.00	$13.00
Purchase #2	$89.47	5.454%	$94.3497	$94.35	$94.35	$94.30
Purchase #3	$184.28	11.859%	$206.1338	$206.13	$206.15	$206.10
Purchase #4	$72.48	13.871%	$82.5337	$82.53	$82.55	$82.50
Purchase #5	$40.48	12.241%	$45.4352	$45.44	$45.45	$45.40
Purchase #6	$207.28	3.781%	$215.1173	$215.12	$215.10	$215.10
Purchase #7	$186.43	3.483%	$192.9234	$192.92	$192.90	$192.90
7 purchase totals =	$792.35		$849.5105	$849.51	$849.50	$849.30