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	$198.78	13.555%	$225.7246	$225.72	$225.70	$225.70
Purchase #2	$34.33	3.541%	$35.5456	$35.55	$35.55	$35.50
Purchase #3	$81.84	4.461%	$85.4909	$85.49	$85.50	$85.50
Purchase #4	$170.59	11.296%	$189.8598	$189.86	$189.85	$189.90
Purchase #5	$171.46	6.587%	$182.7541	$182.75	$182.75	$182.80
Purchase #6	$65.82	8.393%	$71.3443	$71.34	$71.35	$71.30
Purchase #7	$224.40	13.626%	$254.9767	$254.98	$255.00	$255.00
7 purchase totals =	$947.22		$1,045.6960	$1,045.69	$1,045.70	$1,045.70