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	$10.76	6.274%	$11.4351	$11.44	$11.45	$11.40
Purchase #2	$246.79	13.415%	$279.8969	$279.90	$279.90	$279.90
Purchase #3	$165.29	5.270%	$174.0008	$174.00	$174.00	$174.00
Purchase #4	$40.59	6.654%	$43.2909	$43.29	$43.30	$43.30
Purchase #5	$239.48	6.867%	$255.9251	$255.93	$255.95	$255.90
Purchase #6	$179.33	9.715%	$196.7519	$196.75	$196.75	$196.80
Purchase #7	$161.34	6.378%	$171.6303	$171.63	$171.65	$171.60
7 purchase totals =	$1,043.58		$1,132.9310	$1,132.94	$1,133.00	$1,132.90