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	$37.31	10.233%	$41.1279	$41.13	$41.15	$41.10
Purchase #2	$210.27	3.861%	$218.3885	$218.39	$218.40	$218.40
Purchase #3	$77.33	7.140%	$82.8514	$82.85	$82.85	$82.90
Purchase #4	$117.36	6.172%	$124.6035	$124.60	$124.60	$124.60
Purchase #5	$167.59	3.130%	$172.8356	$172.84	$172.85	$172.80
Purchase #6	$112.25	10.429%	$123.9566	$123.96	$123.95	$124.00
Purchase #7	$239.41	11.871%	$267.8304	$267.83	$267.85	$267.80
7 purchase totals =	$961.52		$1,031.5939	$1,031.60	$1,031.65	$1,031.60