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	$46.32	12.146%	$51.946	$51.95	$51.95	$51.90
Purchase #2	$246.88	4.784%	$258.6907	$258.69	$258.70	$258.70
Purchase #3	$232.57	4.292%	$242.5519	$242.55	$242.55	$242.60
Purchase #4	$25.75	12.761%	$29.036	$29.04	$29.05	$29.00
Purchase #5	$90.91	10.629%	$100.5728	$100.57	$100.55	$100.60
Purchase #6	$169.54	3.422%	$175.3417	$175.34	$175.35	$175.30
Purchase #7	$231.61	8.320%	$250.88	$250.88	$250.90	$250.90
7 purchase totals =	$1,043.58		$1,109.0191	$1,109.02	$1,109.05	$1,109.00