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	$221.34	13.404%	$251.0084	$251.01	$251.00	$251.00
Purchase #2	$89.96	3.176%	$92.8171	$92.82	$92.80	$92.80
Purchase #3	$85.86	10.581%	$94.9448	$94.94	$94.95	$94.90
Purchase #4	$20.46	4.493%	$21.3793	$21.38	$21.40	$21.40
Purchase #5	$112.68	5.438%	$118.8075	$118.81	$118.80	$118.80
Purchase #6	$223.61	12.148%	$250.7741	$250.77	$250.75	$250.80
Purchase #7	$233.66	6.482%	$248.8058	$248.81	$248.80	$248.80
7 purchase totals =	$987.57		$1,078.5370	$1,078.54	$1,078.50	$1,078.50