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	$95.53	6.717%	$101.9468	$101.95	$101.95	$101.90
Purchase #2	$38.57	13.247%	$43.6794	$43.68	$43.70	$43.70
Purchase #3	$44.98	7.102%	$48.1745	$48.17	$48.15	$48.20
Purchase #4	$40.52	6.705%	$43.2369	$43.24	$43.25	$43.20
Purchase #5	$168.68	3.653%	$174.8419	$174.84	$174.85	$174.80
Purchase #6	$50.79	6.821%	$54.2544	$54.25	$54.25	$54.30
Purchase #7	$67.56	7.290%	$72.4851	$72.49	$72.50	$72.50
7 purchase totals =	$506.63		$538.6190	$538.62	$538.65	$538.60