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	$227.78	13.719%	$259.0291	$259.03	$259.05	$259.00
Purchase #2	$40.73	6.868%	$43.5273	$43.53	$43.55	$43.50
Purchase #3	$161.78	5.781%	$171.1325	$171.13	$171.15	$171.10
Purchase #4	$227.95	12.539%	$256.5327	$256.53	$256.55	$256.50
Purchase #5	$115.86	8.139%	$125.2898	$125.29	$125.30	$125.30
Purchase #6	$175.57	12.813%	$198.0658	$198.07	$198.05	$198.10
Purchase #7	$90.41	5.656%	$95.5236	$95.52	$95.50	$95.50
7 purchase totals =	$1,040.08		$1,149.1008	$1,149.10	$1,149.15	$1,149.00