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	$190.90	12.353%	$214.4819	$214.48	$214.50	$214.50
Purchase #2	$186.43	5.168%	$196.0647	$196.06	$196.05	$196.10
Purchase #3	$104.91	10.542%	$115.9696	$115.97	$115.95	$116.00
Purchase #4	$165.98	3.316%	$171.4839	$171.48	$171.50	$171.50
Purchase #5	$59.34	7.125%	$63.568	$63.57	$63.55	$63.60
Purchase #6	$46.59	7.785%	$50.217	$50.22	$50.20	$50.20
Purchase #7	$111.78	7.752%	$120.4452	$120.45	$120.45	$120.40
7 purchase totals =	$865.93		$932.2303	$932.23	$932.20	$932.30