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	$132.88	7.396%	$142.7078	$142.71	$142.70	$142.70
Purchase #2	$25.51	6.391%	$27.1403	$27.14	$27.15	$27.10
Purchase #3	$47.68	7.818%	$51.4076	$51.41	$51.40	$51.40
Purchase #4	$129.90	7.656%	$139.8451	$139.85	$139.85	$139.80
Purchase #5	$126.85	3.259%	$130.984	$130.98	$131.00	$131.00
Purchase #6	$76.61	9.772%	$84.0963	$84.10	$84.10	$84.10
Purchase #7	$82.50	10.308%	$91.0041	$91.00	$91.00	$91.00
7 purchase totals =	$621.93		$667.1852	$667.19	$667.20	$667.10