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	$216.97	3.134%	$223.7698	$223.77	$223.75	$223.80
Purchase #2	$6.68	8.807%	$7.2683	$7.27	$7.25	$7.30
Purchase #3	$147.96	9.738%	$162.3683	$162.37	$162.35	$162.40
Purchase #4	$188.83	7.274%	$202.5655	$202.57	$202.55	$202.60
Purchase #5	$95.40	4.677%	$99.8619	$99.86	$99.85	$99.90
Purchase #6	$134.53	5.845%	$142.3933	$142.39	$142.40	$142.40
Purchase #7	$227.72	12.395%	$255.9459	$255.95	$255.95	$255.90
7 purchase totals =	$1,018.09		$1,094.1730	$1,094.18	$1,094.10	$1,094.30