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	$140.61	8.603%	$152.7067	$152.71	$152.70	$152.70
Purchase #2	$138.79	10.851%	$153.8501	$153.85	$153.85	$153.90
Purchase #3	$111.35	11.304%	$123.937	$123.94	$123.95	$123.90
Purchase #4	$169.45	9.746%	$185.9646	$185.96	$185.95	$186.00
Purchase #5	$231.98	12.123%	$260.1029	$260.10	$260.10	$260.10
Purchase #6	$88.32	12.178%	$99.0756	$99.08	$99.10	$99.10
Purchase #7	$221.59	9.613%	$242.8914	$242.89	$242.90	$242.90
7 purchase totals =	$1,102.09		$1,218.5283	$1,218.53	$1,218.55	$1,218.60