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	$249.70	9.442%	$273.2767	$273.28	$273.30	$273.30
Purchase #2	$75.95	3.172%	$78.3591	$78.36	$78.35	$78.40
Purchase #3	$246.46	13.556%	$279.8701	$279.87	$279.85	$279.90
Purchase #4	$12.62	5.237%	$13.2809	$13.28	$13.30	$13.30
Purchase #5	$56.81	3.473%	$58.783	$58.78	$58.80	$58.80
Purchase #6	$137.25	5.313%	$144.5421	$144.54	$144.55	$144.50
Purchase #7	$147.92	13.776%	$168.2975	$168.30	$168.30	$168.30
7 purchase totals =	$926.71		$1,016.4094	$1,016.41	$1,016.45	$1,016.50