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	$87.34	8.709%	$94.9464	$94.95	$94.95	$94.90
Purchase #2	$123.51	6.516%	$131.5579	$131.56	$131.55	$131.60
Purchase #3	$80.32	7.193%	$86.0974	$86.10	$86.10	$86.10
Purchase #4	$186.47	5.582%	$196.8788	$196.88	$196.90	$196.90
Purchase #5	$42.36	12.730%	$47.7524	$47.75	$47.75	$47.80
Purchase #6	$231.60	11.117%	$257.347	$257.35	$257.35	$257.30
Purchase #7	$175.33	3.531%	$181.5209	$181.52	$181.50	$181.50
7 purchase totals =	$926.93		$996.1008	$996.11	$996.10	$996.10