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	$96.62	9.244%	$105.5516	$105.55	$105.55	$105.60
Purchase #2	$143.99	8.260%	$155.8836	$155.88	$155.90	$155.90
Purchase #3	$69.78	8.336%	$75.5969	$75.60	$75.60	$75.60
Purchase #4	$140.51	6.808%	$150.0759	$150.08	$150.10	$150.10
Purchase #5	$164.66	9.544%	$180.3752	$180.38	$180.40	$180.40
Purchase #6	$199.75	11.519%	$222.7592	$222.76	$222.75	$222.80
Purchase #7	$35.93	4.396%	$37.5095	$37.51	$37.50	$37.50
7 purchase totals =	$851.24		$927.7519	$927.76	$927.80	$927.90