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	$194.76	3.119%	$200.8346	$200.83	$200.85	$200.80
Purchase #2	$56.38	13.625%	$64.0618	$64.06	$64.05	$64.10
Purchase #3	$237.25	12.560%	$267.0486	$267.05	$267.05	$267.00
Purchase #4	$229.41	13.270%	$259.8527	$259.85	$259.85	$259.90
Purchase #5	$105.94	10.672%	$117.2459	$117.25	$117.25	$117.20
Purchase #6	$131.72	7.384%	$141.4462	$141.45	$141.45	$141.40
Purchase #7	$86.43	3.788%	$89.704	$89.70	$89.70	$89.70
7 purchase totals =	$1,041.89		$1,140.1938	$1,140.19	$1,140.20	$1,140.10