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	$135.59	3.501%	$140.337	$140.34	$140.35	$140.30
Purchase #2	$38.67	10.586%	$42.7636	$42.76	$42.75	$42.80
Purchase #3	$209.68	8.146%	$226.7605	$226.76	$226.75	$226.80
Purchase #4	$94.30	10.109%	$103.8328	$103.83	$103.85	$103.80
Purchase #5	$29.83	5.164%	$31.3704	$31.37	$31.35	$31.40
Purchase #6	$35.48	11.623%	$39.6038	$39.60	$39.60	$39.60
Purchase #7	$148.87	6.182%	$158.0731	$158.07	$158.05	$158.10
7 purchase totals =	$692.42		$742.7412	$742.73	$742.70	$742.80