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	$161.34	12.390%	$181.33	$181.33	$181.35	$181.30
Purchase #2	$73.25	10.336%	$80.8211	$80.82	$80.80	$80.80
Purchase #3	$43.58	7.566%	$46.8773	$46.88	$46.90	$46.90
Purchase #4	$188.38	5.565%	$198.8633	$198.86	$198.85	$198.90
Purchase #5	$237.53	11.341%	$264.4683	$264.47	$264.45	$264.50
Purchase #6	$72.78	13.682%	$82.7378	$82.74	$82.75	$82.70
Purchase #7	$208.64	8.780%	$226.9586	$226.96	$226.95	$227.00
7 purchase totals =	$985.50		$1,082.0564	$1,082.06	$1,082.05	$1,082.10