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	$59.63	13.627%	$67.7558	$67.76	$67.75	$67.80
Purchase #2	$15.88	12.232%	$17.8224	$17.82	$17.80	$17.80
Purchase #3	$102.92	5.345%	$108.4211	$108.42	$108.40	$108.40
Purchase #4	$114.57	13.139%	$129.6234	$129.62	$129.60	$129.60
Purchase #5	$94.53	6.148%	$100.3417	$100.34	$100.35	$100.30
Purchase #6	$165.70	9.750%	$181.8558	$181.86	$181.85	$181.90
Purchase #7	$78.79	4.745%	$82.5286	$82.53	$82.55	$82.50
7 purchase totals =	$632.02		$688.3488	$688.35	$688.30	$688.30