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	$142.99	5.220%	$150.4541	$150.45	$150.45	$150.50
Purchase #2	$154.34	13.870%	$175.747	$175.75	$175.75	$175.70
Purchase #3	$59.52	11.691%	$66.4785	$66.48	$66.50	$66.50
Purchase #4	$19.26	10.678%	$21.3166	$21.32	$21.30	$21.30
Purchase #5	$216.53	10.636%	$239.5601	$239.56	$239.55	$239.60
Purchase #6	$170.85	8.805%	$185.8933	$185.89	$185.90	$185.90
Purchase #7	$168.50	10.871%	$186.8176	$186.82	$186.80	$186.80
7 purchase totals =	$931.99		$1,026.2672	$1,026.27	$1,026.25	$1,026.30