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	$243.46	3.313%	$251.5258	$251.53	$251.55	$251.50
Purchase #2	$146.99	5.573%	$155.1818	$155.18	$155.20	$155.20
Purchase #3	$111.37	12.189%	$124.9449	$124.94	$124.95	$124.90
Purchase #4	$180.80	9.768%	$198.4605	$198.46	$198.45	$198.50
Purchase #5	$66.65	7.192%	$71.4435	$71.44	$71.45	$71.40
Purchase #6	$188.96	10.861%	$209.4829	$209.48	$209.50	$209.50
Purchase #7	$43.25	5.516%	$45.6357	$45.64	$45.65	$45.60
7 purchase totals =	$981.48		$1,056.6751	$1,056.67	$1,056.75	$1,056.60