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	$137.25	3.159%	$141.5857	$141.59	$141.60	$141.60
Purchase #2	$84.36	13.752%	$95.9612	$95.96	$95.95	$96.00
Purchase #3	$75.45	13.861%	$85.9081	$85.91	$85.90	$85.90
Purchase #4	$87.35	13.140%	$98.8278	$98.83	$98.85	$98.80
Purchase #5	$82.78	6.682%	$88.3114	$88.31	$88.30	$88.30
Purchase #6	$154.75	13.496%	$175.6351	$175.64	$175.65	$175.60
Purchase #7	$108.60	6.721%	$115.899	$115.90	$115.90	$115.90
7 purchase totals =	$730.54		$802.1283	$802.14	$802.15	$802.10