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	$248.59	4.159%	$258.9289	$258.93	$258.95	$258.90
Purchase #2	$103.72	3.109%	$106.9447	$106.94	$106.95	$106.90
Purchase #3	$201.95	7.861%	$217.8253	$217.83	$217.85	$217.80
Purchase #4	$218.49	12.161%	$245.0606	$245.06	$245.05	$245.10
Purchase #5	$152.71	13.227%	$172.909	$172.91	$172.90	$172.90
Purchase #6	$135.96	5.546%	$143.5003	$143.50	$143.50	$143.50
Purchase #7	$61.95	4.668%	$64.8418	$64.84	$64.85	$64.80
7 purchase totals =	$1,123.37		$1,210.0106	$1,210.01	$1,210.05	$1,209.90