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	$206.59	5.437%	$217.8223	$217.82	$217.80	$217.80
Purchase #2	$90.38	11.216%	$100.517	$100.52	$100.50	$100.50
Purchase #3	$82.97	8.822%	$90.2896	$90.29	$90.30	$90.30
Purchase #4	$84.55	8.280%	$91.5507	$91.55	$91.55	$91.60
Purchase #5	$195.69	10.504%	$216.2453	$216.25	$216.25	$216.20
Purchase #6	$141.86	10.643%	$156.9582	$156.96	$156.95	$157.00
Purchase #7	$82.65	6.132%	$87.7181	$87.72	$87.70	$87.70
7 purchase totals =	$884.69		$961.1012	$961.11	$961.05	$961.10