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	$113.86	9.384%	$124.5446	$124.54	$124.55	$124.50
Purchase #2	$196.42	6.320%	$208.8337	$208.83	$208.85	$208.80
Purchase #3	$38.50	6.215%	$40.8928	$40.89	$40.90	$40.90
Purchase #4	$54.71	8.373%	$59.2909	$59.29	$59.30	$59.30
Purchase #5	$168.86	5.247%	$177.7201	$177.72	$177.70	$177.70
Purchase #6	$98.67	3.175%	$101.8028	$101.80	$101.80	$101.80
Purchase #7	$89.31	6.395%	$95.0214	$95.02	$95.00	$95.00
7 purchase totals =	$760.33		$808.1063	$808.09	$808.10	$808.00