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	$44.38	9.863%	$48.7572	$48.76	$48.75	$48.80
Purchase #2	$205.26	12.737%	$231.404	$231.40	$231.40	$231.40
Purchase #3	$186.50	6.482%	$198.5889	$198.59	$198.60	$198.60
Purchase #4	$67.34	8.117%	$72.806	$72.81	$72.80	$72.80
Purchase #5	$171.90	7.424%	$184.6619	$184.66	$184.65	$184.70
Purchase #6	$80.59	12.266%	$90.4752	$90.48	$90.50	$90.50
Purchase #7	$94.66	9.258%	$103.4236	$103.42	$103.40	$103.40
7 purchase totals =	$850.63		$930.1168	$930.12	$930.10	$930.20