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	$239.77	3.241%	$247.5409	$247.54	$247.55	$247.50
Purchase #2	$103.87	5.486%	$109.5683	$109.57	$109.55	$109.60
Purchase #3	$63.35	3.604%	$65.6331	$65.63	$65.65	$65.60
Purchase #4	$75.32	9.640%	$82.5808	$82.58	$82.60	$82.60
Purchase #5	$234.55	10.815%	$259.9166	$259.92	$259.90	$259.90
Purchase #6	$31.96	3.405%	$33.0482	$33.05	$33.05	$33.00
Purchase #7	$192.56	10.691%	$213.1466	$213.15	$213.15	$213.10
7 purchase totals =	$941.38		$1,011.4345	$1,011.44	$1,011.45	$1,011.30