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	$168.81	4.557%	$176.5027	$176.50	$176.50	$176.50
Purchase #2	$107.39	6.609%	$114.4874	$114.49	$114.50	$114.50
Purchase #3	$162.46	11.327%	$180.8618	$180.86	$180.85	$180.90
Purchase #4	$86.98	3.821%	$90.3035	$90.30	$90.30	$90.30
Purchase #5	$192.42	11.869%	$215.2583	$215.26	$215.25	$215.30
Purchase #6	$124.66	6.514%	$132.7804	$132.78	$132.80	$132.80
Purchase #7	$6.53	12.424%	$7.3413	$7.34	$7.35	$7.30
7 purchase totals =	$849.25		$917.5354	$917.53	$917.55	$917.60