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	$74.68	5.245%	$78.597	$78.60	$78.60	$78.60
Purchase #2	$137.93	10.431%	$152.3175	$152.32	$152.30	$152.30
Purchase #3	$37.57	6.807%	$40.1274	$40.13	$40.15	$40.10
Purchase #4	$130.97	9.827%	$143.8404	$143.84	$143.85	$143.80
Purchase #5	$243.47	8.463%	$264.0749	$264.07	$264.05	$264.10
Purchase #6	$113.90	4.284%	$118.7795	$118.78	$118.80	$118.80
Purchase #7	$219.92	3.273%	$227.118	$227.12	$227.10	$227.10
7 purchase totals =	$958.44		$1,024.8547	$1,024.86	$1,024.85	$1,024.80