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	$112.76	9.799%	$123.8094	$123.81	$123.80	$123.80
Purchase #2	$211.79	4.625%	$221.5853	$221.59	$221.60	$221.60
Purchase #3	$218.36	13.232%	$247.2534	$247.25	$247.25	$247.30
Purchase #4	$67.34	8.545%	$73.0942	$73.09	$73.10	$73.10
Purchase #5	$57.88	9.686%	$63.4863	$63.49	$63.50	$63.50
Purchase #6	$221.48	10.102%	$243.8539	$243.85	$243.85	$243.90
Purchase #7	$106.97	5.108%	$112.434	$112.43	$112.45	$112.40
7 purchase totals =	$996.58		$1,085.5165	$1,085.51	$1,085.55	$1,085.60