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	$182.85	11.854%	$204.525	$204.53	$204.55	$204.50
Purchase #2	$31.79	11.343%	$35.3959	$35.40	$35.40	$35.40
Purchase #3	$138.42	9.709%	$151.8592	$151.86	$151.85	$151.90
Purchase #4	$198.81	11.357%	$221.3889	$221.39	$221.40	$221.40
Purchase #5	$143.72	13.310%	$162.8491	$162.85	$162.85	$162.80
Purchase #6	$236.49	10.689%	$261.7684	$261.77	$261.75	$261.80
Purchase #7	$168.69	13.124%	$190.8289	$190.83	$190.85	$190.80
7 purchase totals =	$1,100.77		$1,228.6154	$1,228.63	$1,228.65	$1,228.60