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	$150.60	11.457%	$167.8542	$167.85	$167.85	$167.90
Purchase #2	$44.97	6.753%	$48.0068	$48.01	$48.00	$48.00
Purchase #3	$23.76	7.343%	$25.5047	$25.50	$25.50	$25.50
Purchase #4	$159.94	11.788%	$178.7937	$178.79	$178.80	$178.80
Purchase #5	$216.34	9.200%	$236.2433	$236.24	$236.25	$236.20
Purchase #6	$151.40	9.840%	$166.2978	$166.30	$166.30	$166.30
Purchase #7	$33.69	11.398%	$37.53	$37.53	$37.55	$37.50
7 purchase totals =	$780.70		$860.2305	$860.22	$860.25	$860.20