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	$250.25	4.339%	$261.1083	$261.11	$261.10	$261.10
Purchase #2	$30.96	6.161%	$32.8674	$32.87	$32.85	$32.90
Purchase #3	$40.53	4.408%	$42.3166	$42.32	$42.30	$42.30
Purchase #4	$12.65	13.712%	$14.3846	$14.38	$14.40	$14.40
Purchase #5	$246.31	11.211%	$273.9238	$273.92	$273.90	$273.90
Purchase #6	$205.73	8.401%	$223.0134	$223.01	$223.00	$223.00
Purchase #7	$96.49	3.453%	$99.8218	$99.82	$99.80	$99.80
7 purchase totals =	$882.92		$947.4359	$947.43	$947.35	$947.40