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	$181.93	9.393%	$199.0187	$199.02	$199.00	$199.00
Purchase #2	$238.65	12.447%	$268.3548	$268.35	$268.35	$268.40
Purchase #3	$188.49	10.617%	$208.502	$208.50	$208.50	$208.50
Purchase #4	$50.63	5.629%	$53.48	$53.48	$53.50	$53.50
Purchase #5	$82.97	7.406%	$89.1148	$89.11	$89.10	$89.10
Purchase #6	$164.25	10.309%	$181.1825	$181.18	$181.20	$181.20
Purchase #7	$39.29	11.580%	$43.8398	$43.84	$43.85	$43.80
7 purchase totals =	$946.21		$1,043.4926	$1,043.48	$1,043.50	$1,043.50