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	$150.85	13.840%	$171.7276	$171.73	$171.75	$171.70
Purchase #2	$113.86	4.872%	$119.4073	$119.41	$119.40	$119.40
Purchase #3	$189.26	11.434%	$210.9	$210.90	$210.90	$210.90
Purchase #4	$176.41	12.647%	$198.7206	$198.72	$198.70	$198.70
Purchase #5	$134.60	4.396%	$140.517	$140.52	$140.50	$140.50
Purchase #6	$32.39	13.286%	$36.6933	$36.69	$36.70	$36.70
Purchase #7	$80.80	11.202%	$89.8512	$89.85	$89.85	$89.90
7 purchase totals =	$878.17		$967.8170	$967.82	$967.80	$967.80