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	$24.41	6.299%	$25.9476	$25.95	$25.95	$25.90
Purchase #2	$189.86	13.566%	$215.6164	$215.62	$215.60	$215.60
Purchase #3	$29.54	6.818%	$31.554	$31.55	$31.55	$31.60
Purchase #4	$196.62	3.494%	$203.4899	$203.49	$203.50	$203.50
Purchase #5	$94.63	3.629%	$98.0641	$98.06	$98.05	$98.10
Purchase #6	$67.75	4.457%	$70.7696	$70.77	$70.75	$70.80
Purchase #7	$37.54	12.140%	$42.0974	$42.10	$42.10	$42.10
7 purchase totals =	$640.35		$687.5390	$687.54	$687.50	$687.60