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	$240.96	5.452%	$254.0971	$254.10	$254.10	$254.10
Purchase #2	$28.99	7.208%	$31.0796	$31.08	$31.10	$31.10
Purchase #3	$85.46	11.311%	$95.1264	$95.13	$95.15	$95.10
Purchase #4	$142.32	5.858%	$150.6571	$150.66	$150.65	$150.70
Purchase #5	$41.31	4.538%	$43.1846	$43.18	$43.20	$43.20
Purchase #6	$52.42	12.546%	$58.9966	$59.00	$59.00	$59.00
Purchase #7	$174.52	10.270%	$192.4432	$192.44	$192.45	$192.40
7 purchase totals =	$765.98		$825.5846	$825.59	$825.65	$825.60