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	$140.65	12.655%	$158.4493	$158.45	$158.45	$158.40
Purchase #2	$76.51	8.410%	$82.9445	$82.94	$82.95	$82.90
Purchase #3	$132.84	3.630%	$137.6621	$137.66	$137.65	$137.70
Purchase #4	$168.65	11.487%	$188.0228	$188.02	$188.00	$188.00
Purchase #5	$67.88	3.475%	$70.2388	$70.24	$70.25	$70.20
Purchase #6	$217.54	13.384%	$246.6556	$246.66	$246.65	$246.70
Purchase #7	$119.89	7.110%	$128.4142	$128.41	$128.40	$128.40
7 purchase totals =	$923.96		$1,012.3873	$1,012.38	$1,012.35	$1,012.30