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	$6.89	9.379%	$7.5362	$7.54	$7.55	$7.50
Purchase #2	$215.69	4.471%	$225.3335	$225.33	$225.35	$225.30
Purchase #3	$24.65	4.368%	$25.7267	$25.73	$25.75	$25.70
Purchase #4	$51.67	8.763%	$56.1978	$56.20	$56.20	$56.20
Purchase #5	$122.46	7.387%	$131.5061	$131.51	$131.50	$131.50
Purchase #6	$94.37	10.536%	$104.3128	$104.31	$104.30	$104.30
Purchase #7	$156.96	3.486%	$162.4316	$162.43	$162.45	$162.40
7 purchase totals =	$672.69		$713.0447	$713.05	$713.10	$712.90