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	$192.38	7.349%	$206.518	$206.52	$206.50	$206.50
Purchase #2	$32.63	5.770%	$34.5128	$34.51	$34.50	$34.50
Purchase #3	$139.30	11.311%	$155.0562	$155.06	$155.05	$155.10
Purchase #4	$51.55	4.756%	$54.0017	$54.00	$54.00	$54.00
Purchase #5	$50.78	10.233%	$55.9763	$55.98	$56.00	$56.00
Purchase #6	$249.76	5.774%	$264.1811	$264.18	$264.20	$264.20
Purchase #7	$222.78	4.796%	$233.4645	$233.46	$233.45	$233.50
7 purchase totals =	$939.18		$1,003.7106	$1,003.71	$1,003.70	$1,003.80