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	$83.38	4.427%	$87.0712	$87.07	$87.05	$87.10
Purchase #2	$144.83	5.287%	$152.4872	$152.49	$152.50	$152.50
Purchase #3	$242.58	12.850%	$273.7515	$273.75	$273.75	$273.80
Purchase #4	$117.81	11.688%	$131.5796	$131.58	$131.60	$131.60
Purchase #5	$84.58	5.831%	$89.5119	$89.51	$89.50	$89.50
Purchase #6	$162.71	13.632%	$184.8906	$184.89	$184.90	$184.90
Purchase #7	$158.96	4.134%	$165.5314	$165.53	$165.55	$165.50
7 purchase totals =	$994.85		$1,084.8234	$1,084.82	$1,084.85	$1,084.90