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	$172.90	8.304%	$187.2576	$187.26	$187.25	$187.30
Purchase #2	$158.82	6.206%	$168.6764	$168.68	$168.70	$168.70
Purchase #3	$12.95	4.664%	$13.554	$13.55	$13.55	$13.60
Purchase #4	$77.56	9.639%	$85.036	$85.04	$85.05	$85.00
Purchase #5	$182.75	12.627%	$205.8258	$205.83	$205.85	$205.80
Purchase #6	$81.86	4.697%	$85.705	$85.71	$85.70	$85.70
Purchase #7	$238.53	13.497%	$270.7244	$270.72	$270.70	$270.70
7 purchase totals =	$925.37		$1,016.7792	$1,016.79	$1,016.80	$1,016.80