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	$62.60	3.653%	$64.8868	$64.89	$64.90	$64.90
Purchase #2	$156.65	8.449%	$169.8854	$169.89	$169.90	$169.90
Purchase #3	$66.52	9.210%	$72.6465	$72.65	$72.65	$72.60
Purchase #4	$195.90	10.226%	$215.9327	$215.93	$215.95	$215.90
Purchase #5	$233.31	3.228%	$240.8412	$240.84	$240.85	$240.80
Purchase #6	$131.70	5.756%	$139.2807	$139.28	$139.30	$139.30
Purchase #7	$154.79	3.786%	$160.6503	$160.65	$160.65	$160.70
7 purchase totals =	$1,001.47		$1,064.1236	$1,064.13	$1,064.20	$1,064.10