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	$60.36	10.486%	$66.6893	$66.69	$66.70	$66.70
Purchase #2	$164.55	8.580%	$178.6684	$178.67	$178.65	$178.70
Purchase #3	$191.54	12.366%	$215.2258	$215.23	$215.25	$215.20
Purchase #4	$85.27	3.839%	$88.5435	$88.54	$88.55	$88.50
Purchase #5	$162.45	3.184%	$167.6224	$167.62	$167.60	$167.60
Purchase #6	$235.57	11.151%	$261.8384	$261.84	$261.85	$261.80
Purchase #7	$81.46	5.159%	$85.6625	$85.66	$85.65	$85.70
7 purchase totals =	$981.20		$1,064.2503	$1,064.25	$1,064.25	$1,064.20