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	$39.42	4.816%	$41.3185	$41.32	$41.30	$41.30
Purchase #2	$148.66	10.455%	$164.2024	$164.20	$164.20	$164.20
Purchase #3	$83.29	4.407%	$86.9606	$86.96	$86.95	$87.00
Purchase #4	$243.63	10.193%	$268.4632	$268.46	$268.45	$268.50
Purchase #5	$103.45	7.796%	$111.515	$111.52	$111.50	$111.50
Purchase #6	$131.36	10.807%	$145.5561	$145.56	$145.55	$145.60
Purchase #7	$154.27	13.808%	$175.5716	$175.57	$175.55	$175.60
7 purchase totals =	$904.08		$993.5874	$993.59	$993.50	$993.70