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	$48.71	7.507%	$52.3667	$52.37	$52.35	$52.40
Purchase #2	$99.96	12.290%	$112.2451	$112.25	$112.25	$112.20
Purchase #3	$72.55	8.418%	$78.6573	$78.66	$78.65	$78.70
Purchase #4	$223.44	7.802%	$240.8728	$240.87	$240.85	$240.90
Purchase #5	$34.29	12.202%	$38.4741	$38.47	$38.45	$38.50
Purchase #6	$36.70	10.742%	$40.6423	$40.64	$40.65	$40.60
Purchase #7	$108.94	5.422%	$114.8467	$114.85	$114.85	$114.80
7 purchase totals =	$624.59		$678.1050	$678.11	$678.05	$678.10