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	$217.79	10.677%	$241.0434	$241.04	$241.05	$241.00
Purchase #2	$150.27	11.635%	$167.7539	$167.75	$167.75	$167.80
Purchase #3	$81.76	12.280%	$91.8001	$91.80	$91.80	$91.80
Purchase #4	$149.89	11.782%	$167.55	$167.55	$167.55	$167.60
Purchase #5	$147.67	11.455%	$164.5856	$164.59	$164.60	$164.60
Purchase #6	$85.67	8.394%	$92.8611	$92.86	$92.85	$92.90
Purchase #7	$109.86	9.217%	$119.9858	$119.99	$120.00	$120.00
7 purchase totals =	$942.91		$1,045.5799	$1,045.58	$1,045.60	$1,045.70