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	$33.98	10.185%	$37.4409	$37.44	$37.45	$37.40
Purchase #2	$49.66	9.802%	$54.5277	$54.53	$54.55	$54.50
Purchase #3	$36.56	10.688%	$40.4675	$40.47	$40.45	$40.50
Purchase #4	$174.53	6.664%	$186.1607	$186.16	$186.15	$186.20
Purchase #5	$206.58	3.509%	$213.8289	$213.83	$213.85	$213.80
Purchase #6	$128.69	5.511%	$135.7821	$135.78	$135.80	$135.80
Purchase #7	$117.87	11.571%	$131.5087	$131.51	$131.50	$131.50
7 purchase totals =	$747.87		$799.7165	$799.72	$799.75	$799.70