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	$171.35	6.715%	$182.8562	$182.86	$182.85	$182.90
Purchase #2	$38.96	11.470%	$43.4287	$43.43	$43.45	$43.40
Purchase #3	$155.25	12.474%	$174.6159	$174.62	$174.60	$174.60
Purchase #4	$246.64	8.639%	$267.9472	$267.95	$267.95	$267.90
Purchase #5	$150.54	3.304%	$155.5138	$155.51	$155.50	$155.50
Purchase #6	$57.42	11.660%	$64.1152	$64.12	$64.10	$64.10
Purchase #7	$246.32	9.802%	$270.4643	$270.46	$270.45	$270.50
7 purchase totals =	$1,066.48		$1,158.9413	$1,158.95	$1,158.90	$1,158.90