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	$162.41	4.449%	$169.6356	$169.64	$169.65	$169.60
Purchase #2	$172.41	6.447%	$183.5253	$183.53	$183.55	$183.50
Purchase #3	$222.37	9.662%	$243.8554	$243.86	$243.85	$243.90
Purchase #4	$104.50	3.532%	$108.1909	$108.19	$108.20	$108.20
Purchase #5	$51.34	11.787%	$57.3914	$57.39	$57.40	$57.40
Purchase #6	$13.41	4.523%	$14.0165	$14.02	$14.00	$14.00
Purchase #7	$85.34	5.365%	$89.9185	$89.92	$89.90	$89.90
7 purchase totals =	$811.78		$866.5336	$866.55	$866.55	$866.50