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	$64.32	4.755%	$67.3784	$67.38	$67.40	$67.40
Purchase #2	$50.85	7.308%	$54.5661	$54.57	$54.55	$54.60
Purchase #3	$45.94	3.409%	$47.5061	$47.51	$47.50	$47.50
Purchase #4	$231.29	13.215%	$261.855	$261.86	$261.85	$261.90
Purchase #5	$37.31	5.801%	$39.4744	$39.47	$39.45	$39.50
Purchase #6	$104.34	4.807%	$109.3556	$109.36	$109.35	$109.40
Purchase #7	$190.76	4.615%	$199.5636	$199.56	$199.55	$199.60
7 purchase totals =	$724.81		$779.6992	$779.71	$779.65	$779.90