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	$168.50	8.372%	$182.6068	$182.61	$182.60	$182.60
Purchase #2	$32.91	5.733%	$34.7967	$34.80	$34.80	$34.80
Purchase #3	$241.94	6.121%	$256.7491	$256.75	$256.75	$256.70
Purchase #4	$211.75	6.555%	$225.6302	$225.63	$225.65	$225.60
Purchase #5	$84.76	7.191%	$90.8551	$90.86	$90.85	$90.90
Purchase #6	$112.52	4.295%	$117.3527	$117.35	$117.35	$117.40
Purchase #7	$238.44	4.258%	$248.5928	$248.59	$248.60	$248.60
7 purchase totals =	$1,090.82		$1,156.5834	$1,156.59	$1,156.60	$1,156.60