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	$191.96	6.456%	$204.3529	$204.35	$204.35	$204.40
Purchase #2	$124.89	13.314%	$141.5179	$141.52	$141.50	$141.50
Purchase #3	$153.60	7.208%	$164.6715	$164.67	$164.65	$164.70
Purchase #4	$90.30	6.870%	$96.5036	$96.50	$96.50	$96.50
Purchase #5	$243.54	13.402%	$276.1792	$276.18	$276.20	$276.20
Purchase #6	$87.49	5.188%	$92.029	$92.03	$92.05	$92.00
Purchase #7	$235.43	11.664%	$262.8906	$262.89	$262.90	$262.90
7 purchase totals =	$1,127.21		$1,238.1447	$1,238.14	$1,238.15	$1,238.20