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	$101.77	10.770%	$112.7306	$112.73	$112.75	$112.70
Purchase #2	$45.57	12.872%	$51.4358	$51.44	$51.45	$51.40
Purchase #3	$119.48	9.720%	$131.0935	$131.09	$131.10	$131.10
Purchase #4	$75.74	11.409%	$84.3812	$84.38	$84.40	$84.40
Purchase #5	$101.65	7.533%	$109.3073	$109.31	$109.30	$109.30
Purchase #6	$231.79	4.307%	$241.7732	$241.77	$241.75	$241.80
Purchase #7	$156.90	7.401%	$168.5122	$168.51	$168.50	$168.50
7 purchase totals =	$832.90		$899.2338	$899.23	$899.25	$899.20