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	$89.54	6.587%	$95.438	$95.44	$95.45	$95.40
Purchase #2	$249.78	10.278%	$275.4524	$275.45	$275.45	$275.50
Purchase #3	$143.25	8.678%	$155.6812	$155.68	$155.70	$155.70
Purchase #4	$200.56	3.173%	$206.9238	$206.92	$206.90	$206.90
Purchase #5	$115.98	9.252%	$126.7105	$126.71	$126.70	$126.70
Purchase #6	$198.87	13.574%	$225.8646	$225.86	$225.85	$225.90
Purchase #7	$38.59	9.757%	$42.3552	$42.36	$42.35	$42.40
7 purchase totals =	$1,036.57		$1,128.4257	$1,128.42	$1,128.40	$1,128.50