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	$7.27	4.688%	$7.6108	$7.61	$7.60	$7.60
Purchase #2	$81.90	9.257%	$89.4815	$89.48	$89.50	$89.50
Purchase #3	$34.71	3.816%	$36.0345	$36.03	$36.05	$36.00
Purchase #4	$138.96	12.453%	$156.2647	$156.26	$156.25	$156.30
Purchase #5	$45.88	12.135%	$51.4475	$51.45	$51.45	$51.40
Purchase #6	$179.96	3.253%	$185.8141	$185.81	$185.80	$185.80
Purchase #7	$196.69	11.333%	$218.9809	$218.98	$219.00	$219.00
7 purchase totals =	$685.37		$745.6340	$745.62	$745.65	$745.60