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	$94.36	12.631%	$106.2786	$106.28	$106.30	$106.30
Purchase #2	$228.49	5.865%	$241.8909	$241.89	$241.90	$241.90
Purchase #3	$99.36	5.245%	$104.5714	$104.57	$104.55	$104.60
Purchase #4	$249.50	9.758%	$273.8462	$273.85	$273.85	$273.80
Purchase #5	$150.84	11.709%	$168.5019	$168.50	$168.50	$168.50
Purchase #6	$65.81	12.350%	$73.9375	$73.94	$73.95	$73.90
Purchase #7	$90.81	4.337%	$94.7484	$94.75	$94.75	$94.70
7 purchase totals =	$979.17		$1,063.7749	$1,063.78	$1,063.80	$1,063.70