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	$238.33	3.374%	$246.3713	$246.37	$246.35	$246.40
Purchase #2	$35.89	5.115%	$37.7258	$37.73	$37.75	$37.70
Purchase #3	$64.93	10.720%	$71.8905	$71.89	$71.90	$71.90
Purchase #4	$184.57	6.456%	$196.4858	$196.49	$196.50	$196.50
Purchase #5	$115.55	8.226%	$125.0551	$125.06	$125.05	$125.10
Purchase #6	$131.75	6.211%	$139.933	$139.93	$139.95	$139.90
Purchase #7	$116.95	5.788%	$123.7191	$123.72	$123.70	$123.70
7 purchase totals =	$887.97		$941.1806	$941.19	$941.20	$941.20