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	$59.78	3.337%	$61.7749	$61.77	$61.75	$61.80
Purchase #2	$238.78	11.552%	$266.3639	$266.36	$266.35	$266.40
Purchase #3	$166.98	13.337%	$189.2501	$189.25	$189.25	$189.30
Purchase #4	$212.78	6.347%	$226.2851	$226.29	$226.30	$226.30
Purchase #5	$118.80	5.727%	$125.6037	$125.60	$125.60	$125.60
Purchase #6	$19.57	10.143%	$21.555	$21.56	$21.55	$21.60
Purchase #7	$111.93	6.754%	$119.4898	$119.49	$119.50	$119.50
7 purchase totals =	$928.62		$1,010.3225	$1,010.32	$1,010.30	$1,010.50