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	$209.84	13.811%	$238.821	$238.82	$238.80	$238.80
Purchase #2	$211.90	5.183%	$222.8828	$222.88	$222.90	$222.90
Purchase #3	$33.93	4.655%	$35.5094	$35.51	$35.50	$35.50
Purchase #4	$234.89	13.441%	$266.4616	$266.46	$266.45	$266.50
Purchase #5	$29.64	8.599%	$32.1887	$32.19	$32.20	$32.20
Purchase #6	$49.81	4.212%	$51.908	$51.91	$51.90	$51.90
Purchase #7	$236.74	13.102%	$267.7577	$267.76	$267.75	$267.80
7 purchase totals =	$1,006.75		$1,115.5292	$1,115.53	$1,115.50	$1,115.60