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	$10.69	8.822%	$11.6331	$11.63	$11.65	$11.60
Purchase #2	$131.67	6.618%	$140.3839	$140.38	$140.40	$140.40
Purchase #3	$181.56	3.261%	$187.4807	$187.48	$187.50	$187.50
Purchase #4	$105.40	11.218%	$117.2238	$117.22	$117.20	$117.20
Purchase #5	$232.44	8.336%	$251.8162	$251.82	$251.80	$251.80
Purchase #6	$142.55	4.357%	$148.7609	$148.76	$148.75	$148.80
Purchase #7	$150.63	7.835%	$162.4319	$162.43	$162.45	$162.40
7 purchase totals =	$954.94		$1,019.7305	$1,019.72	$1,019.75	$1,019.70