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	$44.33	6.198%	$47.0776	$47.08	$47.10	$47.10
Purchase #2	$57.35	4.354%	$59.847	$59.85	$59.85	$59.80
Purchase #3	$73.80	6.508%	$78.6029	$78.60	$78.60	$78.60
Purchase #4	$159.51	3.573%	$165.2093	$165.21	$165.20	$165.20
Purchase #5	$64.61	8.204%	$69.9106	$69.91	$69.90	$69.90
Purchase #6	$227.67	8.458%	$246.9263	$246.93	$246.95	$246.90
Purchase #7	$102.37	3.246%	$105.6929	$105.69	$105.70	$105.70
7 purchase totals =	$729.64		$773.2666	$773.27	$773.30	$773.20