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	$184.82	8.707%	$200.9123	$200.91	$200.90	$200.90
Purchase #2	$89.38	5.526%	$94.3191	$94.32	$94.30	$94.30
Purchase #3	$206.51	12.359%	$232.0326	$232.03	$232.05	$232.00
Purchase #4	$50.55	11.458%	$56.342	$56.34	$56.35	$56.30
Purchase #5	$181.38	8.359%	$196.5416	$196.54	$196.55	$196.50
Purchase #6	$169.75	4.406%	$177.2292	$177.23	$177.25	$177.20
Purchase #7	$218.37	3.208%	$225.3753	$225.38	$225.40	$225.40
7 purchase totals =	$1,100.76		$1,182.7521	$1,182.75	$1,182.80	$1,182.60