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	$72.64	13.395%	$82.3701	$82.37	$82.35	$82.40
Purchase #2	$130.72	12.704%	$147.3267	$147.33	$147.35	$147.30
Purchase #3	$62.80	7.672%	$67.618	$67.62	$67.60	$67.60
Purchase #4	$193.78	3.426%	$200.4189	$200.42	$200.40	$200.40
Purchase #5	$18.63	10.229%	$20.5357	$20.54	$20.55	$20.50
Purchase #6	$106.68	11.377%	$118.817	$118.82	$118.80	$118.80
Purchase #7	$24.55	12.284%	$27.5657	$27.57	$27.55	$27.60
7 purchase totals =	$609.80		$664.6521	$664.67	$664.60	$664.60