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	$205.94	10.536%	$227.6378	$227.64	$227.65	$227.60
Purchase #2	$244.98	3.625%	$253.8605	$253.86	$253.85	$253.90
Purchase #3	$235.50	12.713%	$265.4391	$265.44	$265.45	$265.40
Purchase #4	$98.74	7.361%	$106.0083	$106.01	$106.00	$106.00
Purchase #5	$116.54	12.866%	$131.534	$131.53	$131.55	$131.50
Purchase #6	$201.82	9.670%	$221.336	$221.34	$221.35	$221.30
Purchase #7	$69.25	4.779%	$72.5595	$72.56	$72.55	$72.60
7 purchase totals =	$1,172.77		$1,278.3752	$1,278.38	$1,278.40	$1,278.30