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	$44.70	10.272%	$49.2916	$49.29	$49.30	$49.30
Purchase #2	$118.26	11.227%	$131.5371	$131.54	$131.55	$131.50
Purchase #3	$114.83	11.271%	$127.7725	$127.77	$127.75	$127.80
Purchase #4	$215.76	4.514%	$225.4994	$225.50	$225.50	$225.50
Purchase #5	$34.43	6.283%	$36.5932	$36.59	$36.60	$36.60
Purchase #6	$159.98	9.273%	$174.8149	$174.81	$174.80	$174.80
Purchase #7	$176.91	8.412%	$191.7917	$191.79	$191.80	$191.80
7 purchase totals =	$864.87		$937.3004	$937.29	$937.30	$937.30