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	$81.54	13.507%	$92.5536	$92.55	$92.55	$92.60
Purchase #2	$50.84	11.194%	$56.531	$56.53	$56.55	$56.50
Purchase #3	$225.76	5.322%	$237.7749	$237.77	$237.75	$237.80
Purchase #4	$39.41	11.481%	$43.9347	$43.93	$43.95	$43.90
Purchase #5	$34.91	6.217%	$37.0804	$37.08	$37.10	$37.10
Purchase #6	$45.81	13.241%	$51.8757	$51.88	$51.90	$51.90
Purchase #7	$128.32	13.811%	$146.0423	$146.04	$146.05	$146.00
7 purchase totals =	$606.59		$665.7926	$665.78	$665.85	$665.80