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	$186.87	11.499%	$208.3582	$208.36	$208.35	$208.40
Purchase #2	$150.84	5.132%	$158.5811	$158.58	$158.60	$158.60
Purchase #3	$78.38	5.580%	$82.7536	$82.75	$82.75	$82.80
Purchase #4	$191.48	4.334%	$199.7787	$199.78	$199.80	$199.80
Purchase #5	$208.60	3.102%	$215.0708	$215.07	$215.05	$215.10
Purchase #6	$127.73	4.726%	$133.7665	$133.77	$133.75	$133.80
Purchase #7	$11.96	8.234%	$12.9448	$12.94	$12.95	$12.90
7 purchase totals =	$955.86		$1,011.2537	$1,011.25	$1,011.25	$1,011.40