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	$56.71	11.872%	$63.4426	$63.44	$63.45	$63.40
Purchase #2	$169.83	9.169%	$185.4017	$185.40	$185.40	$185.40
Purchase #3	$115.90	10.284%	$127.8192	$127.82	$127.80	$127.80
Purchase #4	$81.98	11.175%	$91.1413	$91.14	$91.15	$91.10
Purchase #5	$185.57	6.840%	$198.263	$198.26	$198.25	$198.30
Purchase #6	$18.63	13.367%	$21.1203	$21.12	$21.10	$21.10
Purchase #7	$28.33	11.390%	$31.5568	$31.56	$31.55	$31.60
7 purchase totals =	$656.95		$718.7449	$718.74	$718.70	$718.70