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	$76.60	11.560%	$85.455	$85.46	$85.45	$85.50
Purchase #2	$85.50	11.844%	$95.6266	$95.63	$95.65	$95.60
Purchase #3	$91.78	13.662%	$104.319	$104.32	$104.30	$104.30
Purchase #4	$35.66	13.421%	$40.4459	$40.45	$40.45	$40.40
Purchase #5	$159.66	5.633%	$168.6536	$168.65	$168.65	$168.70
Purchase #6	$55.36	12.127%	$62.0735	$62.07	$62.05	$62.10
Purchase #7	$13.76	12.730%	$15.5116	$15.51	$15.50	$15.50
7 purchase totals =	$518.32		$572.0852	$572.09	$572.05	$572.10