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	$80.87	3.771%	$83.9196	$83.92	$83.90	$83.90
Purchase #2	$81.58	11.448%	$90.9193	$90.92	$90.90	$90.90
Purchase #3	$67.31	11.719%	$75.1981	$75.20	$75.20	$75.20
Purchase #4	$197.83	13.166%	$223.8763	$223.88	$223.90	$223.90
Purchase #5	$152.31	10.216%	$167.87	$167.87	$167.85	$167.90
Purchase #6	$198.80	9.122%	$216.9345	$216.93	$216.95	$216.90
Purchase #7	$231.43	9.538%	$253.5038	$253.50	$253.50	$253.50
7 purchase totals =	$1,010.13		$1,112.2216	$1,112.22	$1,112.20	$1,112.20