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	$247.90	9.693%	$271.9289	$271.93	$271.95	$271.90
Purchase #2	$123.71	10.607%	$136.8319	$136.83	$136.85	$136.80
Purchase #3	$212.55	5.822%	$224.9247	$224.92	$224.90	$224.90
Purchase #4	$152.93	7.868%	$164.9625	$164.96	$164.95	$165.00
Purchase #5	$221.53	4.302%	$231.0602	$231.06	$231.05	$231.10
Purchase #6	$43.89	8.676%	$47.6979	$47.70	$47.70	$47.70
Purchase #7	$109.86	8.407%	$119.0959	$119.10	$119.10	$119.10
7 purchase totals =	$1,112.37		$1,196.5020	$1,196.50	$1,196.50	$1,196.50