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	$95.88	10.191%	$105.6511	$105.65	$105.65	$105.70
Purchase #2	$204.42	13.715%	$232.4562	$232.46	$232.45	$232.50
Purchase #3	$155.31	8.147%	$167.9631	$167.96	$167.95	$168.00
Purchase #4	$73.78	11.254%	$82.0832	$82.08	$82.10	$82.10
Purchase #5	$63.28	6.729%	$67.5381	$67.54	$67.55	$67.50
Purchase #6	$62.46	10.442%	$68.9821	$68.98	$69.00	$69.00
Purchase #7	$81.25	12.430%	$91.3494	$91.35	$91.35	$91.30
7 purchase totals =	$736.38		$816.0232	$816.02	$816.05	$816.10