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	$204.72	6.270%	$217.5559	$217.56	$217.55	$217.60
Purchase #2	$230.58	4.381%	$240.6817	$240.68	$240.70	$240.70
Purchase #3	$42.91	6.334%	$45.6279	$45.63	$45.65	$45.60
Purchase #4	$121.86	12.590%	$137.2022	$137.20	$137.20	$137.20
Purchase #5	$78.25	10.508%	$86.4725	$86.47	$86.45	$86.50
Purchase #6	$192.28	12.793%	$216.8784	$216.88	$216.90	$216.90
Purchase #7	$57.32	6.183%	$60.8641	$60.86	$60.85	$60.90
7 purchase totals =	$927.92		$1,005.2827	$1,005.28	$1,005.30	$1,005.40