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	$200.39	13.475%	$227.3926	$227.39	$227.40	$227.40
Purchase #2	$206.58	12.733%	$232.8838	$232.88	$232.90	$232.90
Purchase #3	$83.64	7.455%	$89.8754	$89.88	$89.90	$89.90
Purchase #4	$237.52	11.700%	$265.3098	$265.31	$265.30	$265.30
Purchase #5	$36.59	10.729%	$40.5157	$40.52	$40.50	$40.50
Purchase #6	$16.68	3.327%	$17.2349	$17.23	$17.25	$17.20
Purchase #7	$174.45	6.351%	$185.5293	$185.53	$185.55	$185.50
7 purchase totals =	$955.85		$1,058.7415	$1,058.74	$1,058.80	$1,058.70