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	$40.34	8.710%	$43.8536	$43.85	$43.85	$43.90
Purchase #2	$93.69	6.816%	$100.0759	$100.08	$100.10	$100.10
Purchase #3	$82.36	5.110%	$86.5686	$86.57	$86.55	$86.60
Purchase #4	$141.68	7.456%	$152.2437	$152.24	$152.25	$152.20
Purchase #5	$215.78	11.634%	$240.8838	$240.88	$240.90	$240.90
Purchase #6	$105.44	13.464%	$119.6364	$119.64	$119.65	$119.60
Purchase #7	$62.88	7.867%	$67.8268	$67.83	$67.85	$67.80
7 purchase totals =	$742.17		$811.0888	$811.09	$811.15	$811.10