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	$226.97	13.501%	$257.6132	$257.61	$257.60	$257.60
Purchase #2	$135.91	12.215%	$152.5114	$152.51	$152.50	$152.50
Purchase #3	$125.79	9.623%	$137.8948	$137.89	$137.90	$137.90
Purchase #4	$222.93	8.492%	$241.8612	$241.86	$241.85	$241.90
Purchase #5	$148.75	13.326%	$168.5724	$168.57	$168.55	$168.60
Purchase #6	$168.27	13.145%	$190.3891	$190.39	$190.40	$190.40
Purchase #7	$182.78	8.485%	$198.2889	$198.29	$198.30	$198.30
7 purchase totals =	$1,211.40		$1,347.1310	$1,347.12	$1,347.10	$1,347.20