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	$67.98	7.754%	$73.2512	$73.25	$73.25	$73.30
Purchase #2	$98.30	10.820%	$108.9361	$108.94	$108.95	$108.90
Purchase #3	$39.54	13.442%	$44.855	$44.86	$44.85	$44.90
Purchase #4	$152.61	7.586%	$164.187	$164.19	$164.20	$164.20
Purchase #5	$45.72	12.861%	$51.6	$51.60	$51.60	$51.60
Purchase #6	$55.66	6.702%	$59.3903	$59.39	$59.40	$59.40
Purchase #7	$112.77	7.825%	$121.5943	$121.59	$121.60	$121.60
7 purchase totals =	$572.58		$623.8139	$623.82	$623.85	$623.90