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	$162.27	5.605%	$171.3652	$171.37	$171.35	$171.40
Purchase #2	$161.75	7.821%	$174.4005	$174.40	$174.40	$174.40
Purchase #3	$142.68	5.511%	$150.5431	$150.54	$150.55	$150.50
Purchase #4	$120.94	3.661%	$125.3676	$125.37	$125.35	$125.40
Purchase #5	$43.80	8.448%	$47.5002	$47.50	$47.50	$47.50
Purchase #6	$35.52	7.663%	$38.2419	$38.24	$38.25	$38.20
Purchase #7	$37.39	12.578%	$42.0929	$42.09	$42.10	$42.10
7 purchase totals =	$704.35		$749.5114	$749.51	$749.50	$749.50