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	$163.64	9.767%	$179.6227	$179.62	$179.60	$179.60
Purchase #2	$215.60	12.178%	$241.8558	$241.86	$241.85	$241.90
Purchase #3	$54.61	8.427%	$59.212	$59.21	$59.20	$59.20
Purchase #4	$98.29	11.478%	$109.5717	$109.57	$109.55	$109.60
Purchase #5	$7.71	8.798%	$8.3883	$8.39	$8.40	$8.40
Purchase #6	$35.78	11.154%	$39.7709	$39.77	$39.75	$39.80
Purchase #7	$178.81	11.780%	$199.8738	$199.87	$199.85	$199.90
7 purchase totals =	$754.44		$838.2952	$838.29	$838.20	$838.40