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	$244.63	4.367%	$255.313	$255.31	$255.30	$255.30
Purchase #2	$45.25	5.813%	$47.8804	$47.88	$47.90	$47.90
Purchase #3	$160.31	9.126%	$174.9399	$174.94	$174.95	$174.90
Purchase #4	$85.80	4.355%	$89.5366	$89.54	$89.55	$89.50
Purchase #5	$38.26	7.715%	$41.2118	$41.21	$41.20	$41.20
Purchase #6	$11.62	10.434%	$12.8324	$12.83	$12.85	$12.80
Purchase #7	$49.52	4.476%	$51.7365	$51.74	$51.75	$51.70
7 purchase totals =	$635.39		$673.4506	$673.45	$673.50	$673.30