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	$158.61	8.427%	$171.9761	$171.98	$172.00	$172.00
Purchase #2	$40.82	12.725%	$46.0143	$46.01	$46.00	$46.00
Purchase #3	$248.57	9.510%	$272.209	$272.21	$272.20	$272.20
Purchase #4	$230.31	7.301%	$247.1249	$247.12	$247.10	$247.10
Purchase #5	$54.97	12.371%	$61.7703	$61.77	$61.75	$61.80
Purchase #6	$39.63	9.873%	$43.5427	$43.54	$43.55	$43.50
Purchase #7	$167.93	4.395%	$175.3105	$175.31	$175.30	$175.30
7 purchase totals =	$940.84		$1,017.9478	$1,017.94	$1,017.90	$1,017.90