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	$116.55	12.705%	$131.3577	$131.36	$131.35	$131.40
Purchase #2	$34.41	10.786%	$38.1215	$38.12	$38.10	$38.10
Purchase #3	$149.32	13.843%	$169.9904	$169.99	$170.00	$170.00
Purchase #4	$221.80	3.440%	$229.4299	$229.43	$229.45	$229.40
Purchase #5	$141.41	3.115%	$145.8149	$145.81	$145.80	$145.80
Purchase #6	$180.55	5.846%	$191.105	$191.11	$191.10	$191.10
Purchase #7	$230.33	6.208%	$244.6289	$244.63	$244.65	$244.60
7 purchase totals =	$1,074.37		$1,150.4483	$1,150.45	$1,150.45	$1,150.40