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	$56.35	11.571%	$62.8703	$62.87	$62.85	$62.90
Purchase #2	$114.81	5.180%	$120.7572	$120.76	$120.75	$120.80
Purchase #3	$133.97	5.174%	$140.9016	$140.90	$140.90	$140.90
Purchase #4	$134.66	3.499%	$139.3718	$139.37	$139.35	$139.40
Purchase #5	$190.48	3.112%	$196.4077	$196.41	$196.40	$196.40
Purchase #6	$26.63	6.528%	$28.3684	$28.37	$28.35	$28.40
Purchase #7	$213.39	5.489%	$225.103	$225.10	$225.10	$225.10
7 purchase totals =	$870.29		$913.7800	$913.78	$913.70	$913.90