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	$53.71	8.568%	$58.3119	$58.31	$58.30	$58.30
Purchase #2	$37.56	8.719%	$40.8349	$40.83	$40.85	$40.80
Purchase #3	$100.76	12.177%	$113.0295	$113.03	$113.05	$113.00
Purchase #4	$102.98	10.113%	$113.3944	$113.39	$113.40	$113.40
Purchase #5	$121.59	12.564%	$136.8666	$136.87	$136.85	$136.90
Purchase #6	$50.91	5.625%	$53.7737	$53.77	$53.75	$53.80
Purchase #7	$174.25	13.805%	$198.3052	$198.31	$198.30	$198.30
7 purchase totals =	$641.76		$714.5162	$714.51	$714.50	$714.50