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	$43.67	11.383%	$48.641	$48.64	$48.65	$48.60
Purchase #2	$24.35	11.357%	$27.1154	$27.12	$27.10	$27.10
Purchase #3	$52.33	13.666%	$59.4814	$59.48	$59.50	$59.50
Purchase #4	$68.76	3.517%	$71.1783	$71.18	$71.20	$71.20
Purchase #5	$147.54	10.821%	$163.5053	$163.51	$163.50	$163.50
Purchase #6	$69.96	7.280%	$75.0531	$75.05	$75.05	$75.10
Purchase #7	$146.28	13.214%	$165.6094	$165.61	$165.60	$165.60
7 purchase totals =	$552.89		$610.5839	$610.59	$610.60	$610.60