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	$30.59	4.439%	$31.9479	$31.95	$31.95	$31.90
Purchase #2	$78.77	5.256%	$82.9102	$82.91	$82.90	$82.90
Purchase #3	$23.83	5.681%	$25.1838	$25.18	$25.20	$25.20
Purchase #4	$53.39	13.365%	$60.5256	$60.53	$60.55	$60.50
Purchase #5	$85.85	5.822%	$90.8482	$90.85	$90.85	$90.80
Purchase #6	$203.74	6.577%	$217.14	$217.14	$217.15	$217.10
Purchase #7	$168.32	13.367%	$190.8193	$190.82	$190.80	$190.80
7 purchase totals =	$644.49		$699.3750	$699.38	$699.40	$699.20