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	$150.66	10.402%	$166.3317	$166.33	$166.35	$166.30
Purchase #2	$6.61	13.820%	$7.5235	$7.52	$7.50	$7.50
Purchase #3	$162.45	4.199%	$169.2713	$169.27	$169.25	$169.30
Purchase #4	$37.37	7.157%	$40.0446	$40.04	$40.05	$40.00
Purchase #5	$220.59	11.870%	$246.774	$246.77	$246.75	$246.80
Purchase #6	$132.65	7.436%	$142.5139	$142.51	$142.50	$142.50
Purchase #7	$135.37	8.317%	$146.6287	$146.63	$146.65	$146.60
7 purchase totals =	$845.70		$919.0877	$919.07	$919.05	$919.00