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	$167.46	8.625%	$181.9034	$181.90	$181.90	$181.90
Purchase #2	$232.89	6.746%	$248.6008	$248.60	$248.60	$248.60
Purchase #3	$11.99	3.178%	$12.371	$12.37	$12.35	$12.40
Purchase #4	$69.80	4.444%	$72.9019	$72.90	$72.90	$72.90
Purchase #5	$61.45	10.132%	$67.6761	$67.68	$67.70	$67.70
Purchase #6	$99.90	3.102%	$102.9989	$103.00	$103.00	$103.00
Purchase #7	$120.27	3.533%	$124.5191	$124.52	$124.50	$124.50
7 purchase totals =	$763.76		$810.9712	$810.97	$810.95	$811.00