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	$103.75	12.151%	$116.3567	$116.36	$116.35	$116.40
Purchase #2	$95.63	4.540%	$99.9716	$99.97	$99.95	$100.00
Purchase #3	$7.37	11.672%	$8.2302	$8.23	$8.25	$8.20
Purchase #4	$221.50	12.396%	$248.9571	$248.96	$248.95	$249.00
Purchase #5	$31.32	5.796%	$33.1353	$33.14	$33.15	$33.10
Purchase #6	$83.45	7.600%	$89.7922	$89.79	$89.80	$89.80
Purchase #7	$49.69	11.820%	$55.5634	$55.56	$55.55	$55.60
7 purchase totals =	$592.71		$652.0065	$652.01	$652.00	$652.10