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	$85.41	4.837%	$89.5413	$89.54	$89.55	$89.50
Purchase #2	$91.82	11.727%	$102.5877	$102.59	$102.60	$102.60
Purchase #3	$162.95	8.733%	$177.1804	$177.18	$177.20	$177.20
Purchase #4	$97.41	12.238%	$109.331	$109.33	$109.35	$109.30
Purchase #5	$244.47	6.139%	$259.478	$259.48	$259.50	$259.50
Purchase #6	$213.81	5.527%	$225.6273	$225.63	$225.65	$225.60
Purchase #7	$179.88	11.606%	$200.7569	$200.76	$200.75	$200.80
7 purchase totals =	$1,075.75		$1,164.5026	$1,164.51	$1,164.60	$1,164.50