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	$246.84	7.433%	$265.1876	$265.19	$265.20	$265.20
Purchase #2	$122.39	7.832%	$131.9756	$131.98	$132.00	$132.00
Purchase #3	$212.96	6.436%	$226.6661	$226.67	$226.65	$226.70
Purchase #4	$53.96	10.410%	$59.5772	$59.58	$59.60	$59.60
Purchase #5	$71.69	9.447%	$78.4626	$78.46	$78.45	$78.50
Purchase #6	$200.78	4.832%	$210.4817	$210.48	$210.50	$210.50
Purchase #7	$159.85	12.545%	$179.9032	$179.90	$179.90	$179.90
7 purchase totals =	$1,068.47		$1,152.2540	$1,152.26	$1,152.30	$1,152.40