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	$168.56	11.405%	$187.7843	$187.78	$187.80	$187.80
Purchase #2	$116.36	6.529%	$123.9571	$123.96	$123.95	$124.00
Purchase #3	$55.56	7.645%	$59.8076	$59.81	$59.80	$59.80
Purchase #4	$120.89	8.434%	$131.0859	$131.09	$131.10	$131.10
Purchase #5	$33.69	4.750%	$35.2903	$35.29	$35.30	$35.30
Purchase #6	$94.82	3.124%	$97.7822	$97.78	$97.80	$97.80
Purchase #7	$80.29	9.382%	$87.8228	$87.82	$87.80	$87.80
7 purchase totals =	$670.17		$723.5302	$723.53	$723.55	$723.60