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	$183.83	6.750%	$196.2385	$196.24	$196.25	$196.20
Purchase #2	$126.89	11.555%	$141.5521	$141.55	$141.55	$141.60
Purchase #3	$78.78	9.549%	$86.3027	$86.30	$86.30	$86.30
Purchase #4	$245.72	7.710%	$264.665	$264.67	$264.65	$264.70
Purchase #5	$195.63	4.182%	$203.8112	$203.81	$203.80	$203.80
Purchase #6	$91.50	3.780%	$94.9587	$94.96	$94.95	$95.00
Purchase #7	$228.66	5.526%	$241.2958	$241.30	$241.30	$241.30
7 purchase totals =	$1,151.01		$1,228.8240	$1,228.83	$1,228.80	$1,228.90