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	$226.96	12.511%	$255.355	$255.36	$255.35	$255.40
Purchase #2	$158.50	5.276%	$166.8625	$166.86	$166.85	$166.90
Purchase #3	$166.82	12.438%	$187.5691	$187.57	$187.55	$187.60
Purchase #4	$127.47	9.488%	$139.5644	$139.56	$139.55	$139.60
Purchase #5	$191.29	4.850%	$200.5676	$200.57	$200.55	$200.60
Purchase #6	$73.93	12.408%	$83.1032	$83.10	$83.10	$83.10
Purchase #7	$172.69	4.311%	$180.1347	$180.13	$180.15	$180.10
7 purchase totals =	$1,117.66		$1,213.1565	$1,213.15	$1,213.10	$1,213.30