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	$229.94	11.717%	$256.8821	$256.88	$256.90	$256.90
Purchase #2	$47.73	8.278%	$51.6811	$51.68	$51.70	$51.70
Purchase #3	$216.48	9.231%	$236.4633	$236.46	$236.45	$236.50
Purchase #4	$201.76	9.464%	$220.8546	$220.85	$220.85	$220.90
Purchase #5	$80.32	3.179%	$82.8734	$82.87	$82.85	$82.90
Purchase #6	$150.94	11.385%	$168.1245	$168.12	$168.10	$168.10
Purchase #7	$91.47	5.483%	$96.4853	$96.49	$96.50	$96.50
7 purchase totals =	$1,018.64		$1,113.3643	$1,113.35	$1,113.35	$1,113.50