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	$219.66	5.396%	$231.5129	$231.51	$231.50	$231.50
Purchase #2	$131.40	6.446%	$139.87	$139.87	$139.85	$139.90
Purchase #3	$38.94	11.265%	$43.3266	$43.33	$43.35	$43.30
Purchase #4	$224.46	11.874%	$251.1124	$251.11	$251.10	$251.10
Purchase #5	$230.34	3.361%	$238.0817	$238.08	$238.10	$238.10
Purchase #6	$76.51	11.128%	$85.024	$85.02	$85.00	$85.00
Purchase #7	$154.32	11.300%	$171.7582	$171.76	$171.75	$171.80
7 purchase totals =	$1,075.63		$1,160.6858	$1,160.68	$1,160.65	$1,160.70