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	$44.88	6.538%	$47.8143	$47.81	$47.80	$47.80
Purchase #2	$208.30	4.603%	$217.888	$217.89	$217.90	$217.90
Purchase #3	$209.47	7.865%	$225.9448	$225.94	$225.95	$225.90
Purchase #4	$96.52	4.302%	$100.6723	$100.67	$100.65	$100.70
Purchase #5	$229.44	9.486%	$251.2047	$251.20	$251.20	$251.20
Purchase #6	$36.72	10.412%	$40.5433	$40.54	$40.55	$40.50
Purchase #7	$249.90	12.638%	$281.4824	$281.48	$281.50	$281.50
7 purchase totals =	$1,075.23		$1,165.5498	$1,165.53	$1,165.55	$1,165.50