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	$98.56	3.402%	$101.913	$101.91	$101.90	$101.90
Purchase #2	$112.58	10.485%	$124.384	$124.38	$124.40	$124.40
Purchase #3	$36.55	8.303%	$39.5847	$39.58	$39.60	$39.60
Purchase #4	$147.49	7.760%	$158.9352	$158.94	$158.95	$158.90
Purchase #5	$147.71	3.161%	$152.3791	$152.38	$152.40	$152.40
Purchase #6	$120.42	13.337%	$136.4804	$136.48	$136.50	$136.50
Purchase #7	$29.61	7.492%	$31.8284	$31.83	$31.85	$31.80
7 purchase totals =	$692.92		$745.5048	$745.50	$745.60	$745.50