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	$189.85	13.171%	$214.8551	$214.86	$214.85	$214.90
Purchase #2	$200.63	11.523%	$223.7486	$223.75	$223.75	$223.70
Purchase #3	$140.63	7.644%	$151.3798	$151.38	$151.40	$151.40
Purchase #4	$111.98	6.509%	$119.2688	$119.27	$119.25	$119.30
Purchase #5	$106.88	11.653%	$119.3347	$119.33	$119.35	$119.30
Purchase #6	$88.48	8.536%	$96.0327	$96.03	$96.05	$96.00
Purchase #7	$77.43	11.632%	$86.4367	$86.44	$86.45	$86.40
7 purchase totals =	$915.88		$1,011.0564	$1,011.06	$1,011.10	$1,011.00