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	$120.30	9.260%	$131.4398	$131.44	$131.45	$131.40
Purchase #2	$29.33	9.813%	$32.2082	$32.21	$32.20	$32.20
Purchase #3	$49.36	5.184%	$51.9188	$51.92	$51.90	$51.90
Purchase #4	$53.84	5.672%	$56.8938	$56.89	$56.90	$56.90
Purchase #5	$80.98	10.176%	$89.2205	$89.22	$89.20	$89.20
Purchase #6	$193.81	10.397%	$213.9604	$213.96	$213.95	$214.00
Purchase #7	$128.40	4.782%	$134.5401	$134.54	$134.55	$134.50
7 purchase totals =	$656.02		$710.1816	$710.18	$710.15	$710.10