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	$227.94	4.657%	$238.5552	$238.56	$238.55	$238.60
Purchase #2	$10.59	5.866%	$11.2112	$11.21	$11.20	$11.20
Purchase #3	$85.31	4.454%	$89.1097	$89.11	$89.10	$89.10
Purchase #4	$166.92	4.579%	$174.5633	$174.56	$174.55	$174.60
Purchase #5	$143.62	8.151%	$155.3265	$155.33	$155.35	$155.30
Purchase #6	$160.88	4.425%	$167.9989	$168.00	$168.00	$168.00
Purchase #7	$41.61	11.435%	$46.3681	$46.37	$46.35	$46.40
7 purchase totals =	$836.87		$883.1329	$883.14	$883.10	$883.20