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	$125.64	11.546%	$140.1464	$140.15	$140.15	$140.10
Purchase #2	$197.56	12.531%	$222.3162	$222.32	$222.30	$222.30
Purchase #3	$37.88	5.141%	$39.8274	$39.83	$39.85	$39.80
Purchase #4	$225.25	5.533%	$237.7131	$237.71	$237.70	$237.70
Purchase #5	$23.43	13.214%	$26.526	$26.53	$26.55	$26.50
Purchase #6	$111.31	7.736%	$119.9209	$119.92	$119.90	$119.90
Purchase #7	$174.92	12.238%	$196.3267	$196.33	$196.35	$196.30
7 purchase totals =	$895.99		$982.7767	$982.79	$982.80	$982.60