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	$81.30	6.261%	$86.3902	$86.39	$86.40	$86.40
Purchase #2	$228.80	4.231%	$238.4805	$238.48	$238.50	$238.50
Purchase #3	$146.95	5.230%	$154.6355	$154.64	$154.65	$154.60
Purchase #4	$230.46	3.377%	$238.2426	$238.24	$238.25	$238.20
Purchase #5	$220.61	3.268%	$227.8195	$227.82	$227.80	$227.80
Purchase #6	$145.66	4.437%	$152.1229	$152.12	$152.10	$152.10
Purchase #7	$7.97	3.797%	$8.2726	$8.27	$8.25	$8.30
7 purchase totals =	$1,061.75		$1,105.9638	$1,105.96	$1,105.95	$1,105.90